Home  
Site Partners: SpotterGuides Veloce Books  
Related Sites: Your Link Here  

Go Back   TenTenths Motorsport Forum > Racing Talk > Racers Forum

Reply
 
Thread Tools Display Modes
Old 25 Jul 2009, 21:53 (Ref:2508017)   #1
Andrew Mitchell
Rookie
 
Join Date: Jul 2009
Posts: 18
Andrew Mitchell should be qualifying in the top 10 on the grid
Finding the correct tyre pressures for dunlop r5's

I have a Bristol special with Dunlop 550-16 r5 crossply racing tyres ,the car weight is 830kg and it tends to oversteer as you would expect with a live axle ,does anyone have any ideas on the best tyre pressures for the track? Andrew.
Andrew Mitchell is offline  
Quote
Old 26 Jul 2009, 10:25 (Ref:2508245)   #2
GORDON STREETER
Veteran
 
GORDON STREETER's Avatar
 
Join Date: Nov 2006
Spain
Kent+Mojacar Spain, but not always ?
Posts: 9,400
GORDON STREETER is going for a new world record!GORDON STREETER is going for a new world record!GORDON STREETER is going for a new world record!GORDON STREETER is going for a new world record!GORDON STREETER is going for a new world record!GORDON STREETER is going for a new world record!GORDON STREETER is going for a new world record!
Not having any dealings with the type of car involved all that I would say is use a pyrometer to find out whats happening, and then decrease the front tyre pressures a couple of pounds and increase the rears by the same amount a few times to get a feeling if its altering anything.
You can play around like this, but normally you will find that it will only make a marginal difference and you should be looking at a suspension change like spring rates/anti roll bars/ toe setting/shock absorber settings etc.
Is it a steady state oversteer or only in slow or fast corners ?
Welcome to the Forum Andrew
GORDON STREETER is online now  
__________________
Balls of steel (knob of butter) They're Asking For Larkins. ( Proper beer) not you're Eurofizz crap. Hace más calor en España. Me han conocido a hablar un montón cojones! Send any cheques and cash to PO box 1 Lagos Nigeria Africa !
Quote
Old 26 Jul 2009, 12:09 (Ref:2508285)   #3
Andrew Mitchell
Rookie
 
Join Date: Jul 2009
Posts: 18
Andrew Mitchell should be qualifying in the top 10 on the grid
The oversteer seems constant,i get a bit more as you would expect in 3rd than 4th gear .I only finished building the car earlier this year the first time I went out the oversteer was terrible and after stiffening the front transverse leaf suspension and softening the rear torsion bar suspension the car was going 5 seconds per lap faster ,the shocks are soft on the back and hard on the front .I have found a larger anti roll bar to try on the front but I am starting to end up with two separate halfs to the car a hard one at the front and a soft one at the back,so I am looking looking different ways to get understeer with getting an even larger stifness differencial.The car is getting close to balanced but i can't get the power on as much as I would like out of the corners (bearing in mind it's only 150bhp) .I am hoping if I can find the ideal rear tyre pressure the front could be higher or lower and I will get understeer ,Or may be I could try to get a bit of toe in out of the live axle ( this could cause mechanical problems) any suggestions?
Andrew Mitchell is offline  
Quote
Old 27 Jul 2009, 12:14 (Ref:2509121)   #4
GORDON STREETER
Veteran
 
GORDON STREETER's Avatar
 
Join Date: Nov 2006
Spain
Kent+Mojacar Spain, but not always ?
Posts: 9,400
GORDON STREETER is going for a new world record!GORDON STREETER is going for a new world record!GORDON STREETER is going for a new world record!GORDON STREETER is going for a new world record!GORDON STREETER is going for a new world record!GORDON STREETER is going for a new world record!GORDON STREETER is going for a new world record!
Mmmm, you have obviously tried the accepted ways to induce understeer that obviously made it more drivable, and the next step is to try the bigger front bar as you already have it.
As I said, not knowing anything about that particular car, you have more knowledge than me but do you know how they originally handled ?
I wouldn't have thought that they were built with inherent oversteer, as you have found out an oversteering car is far more difficult to drive on the limit.
Its always a compromise to get a car to go neutral to understeer, and without making major suspension design changes to a point you can only "unstick" the end that's the problem by stiffening it up .
You might get over the problem using different width tyres back and front but availability and eligibility would probably put a stop to that.
Try the bar first.
I am not a suspension "guru "and hopefully another poster will pop in with some ideas
GORDON STREETER is online now  
__________________
Balls of steel (knob of butter) They're Asking For Larkins. ( Proper beer) not you're Eurofizz crap. Hace más calor en España. Me han conocido a hablar un montón cojones! Send any cheques and cash to PO box 1 Lagos Nigeria Africa !
Quote
Old 27 Jul 2009, 20:56 (Ref:2509482)   #5
Andrew Mitchell
Rookie
 
Join Date: Jul 2009
Posts: 18
Andrew Mitchell should be qualifying in the top 10 on the grid
Thanks Gordon . The car is a special I built myself using a space frame ,putting the suspension ,axle , gearbox and engine from an old Bristol 401 into the frame and making an aluminium body for it.The front suspension is transverse leaf and the rear is tosion bar live axle with a watts linkage.Bristols were a little oversteery so I moved the engine back so the front pulley is 14 inches behind the front wheel centre line making it sort of mid engined.the fuel tanks are under the floor in the centre of the car.So as you can see I'm on my own here,with a little help from my freinds. The car is nearly there ,which is a miracle considering what I have been up to,it;s just that final bit.Andrew.
Andrew Mitchell is offline  
Quote
Old 27 Jul 2009, 23:27 (Ref:2509574)   #6
GORDON STREETER
Veteran
 
GORDON STREETER's Avatar
 
Join Date: Nov 2006
Spain
Kent+Mojacar Spain, but not always ?
Posts: 9,400
GORDON STREETER is going for a new world record!GORDON STREETER is going for a new world record!GORDON STREETER is going for a new world record!GORDON STREETER is going for a new world record!GORDON STREETER is going for a new world record!GORDON STREETER is going for a new world record!GORDON STREETER is going for a new world record!
What type of front suspension has it got with the transverse leaf spring ?
Whatever, the front wants to toe in and so does the rear. Toe out on the rear will cause excessive oversteer with the power on. Have you put a tracking gauge on the rear ?

On my own car I use an adjustable front ARB and can make it over or understeer at the two extreme settings, but this took a bit of time to find the correct size for a start.

Last edited by GORDON STREETER; 27 Jul 2009 at 23:47.
GORDON STREETER is online now  
__________________
Balls of steel (knob of butter) They're Asking For Larkins. ( Proper beer) not you're Eurofizz crap. Hace más calor en España. Me han conocido a hablar un montón cojones! Send any cheques and cash to PO box 1 Lagos Nigeria Africa !
Quote
Old 28 Jul 2009, 15:22 (Ref:2510011)   #7
phoenix
Veteran
 
phoenix's Avatar
 
Join Date: Jul 2005
European Union
Posts: 1,981
phoenix should be qualifying in the top 5 on the gridphoenix should be qualifying in the top 5 on the grid
Hi

I believe that the 401 weighed in at 2760lbs or about 1245kg (another reference says 2786lb which is about 1266kg). Do you know what the front and rear axle weights of the original car were?

Next, do you know the front and rear axle weights of your 'special'?

I suspect that the front/rear springing of your (presumably) light weight special is out of balance and that the rear spring(s) need to be softened, or the front spring stiffened to compensate for the new, lighter chassis, bodywork and different weight distribution.

I also think that if the car was over-steery before moving the engine back will have made the situation worse, not better; a forward weight bias usually gives understeer and reducing that bias, by moving the engine back, would normally reduce understeer.

If you can come up with some numbers it will help to clarify what might be happening.
phoenix is offline  
Quote
Old 28 Jul 2009, 16:47 (Ref:2510057)   #8
GORDON STREETER
Veteran
 
GORDON STREETER's Avatar
 
Join Date: Nov 2006
Spain
Kent+Mojacar Spain, but not always ?
Posts: 9,400
GORDON STREETER is going for a new world record!GORDON STREETER is going for a new world record!GORDON STREETER is going for a new world record!GORDON STREETER is going for a new world record!GORDON STREETER is going for a new world record!GORDON STREETER is going for a new world record!GORDON STREETER is going for a new world record!
phoenix, this sounds like a real "seat of your pants" beast to tame, but I bet its not as much of a handful as the Auto Union type C was with oversteer
GORDON STREETER is online now  
__________________
Balls of steel (knob of butter) They're Asking For Larkins. ( Proper beer) not you're Eurofizz crap. Hace más calor en España. Me han conocido a hablar un montón cojones! Send any cheques and cash to PO box 1 Lagos Nigeria Africa !
Quote
Old 28 Jul 2009, 17:35 (Ref:2510087)   #9
phoenix
Veteran
 
phoenix's Avatar
 
Join Date: Jul 2005
European Union
Posts: 1,981
phoenix should be qualifying in the top 5 on the gridphoenix should be qualifying in the top 5 on the grid
Quote:
Originally Posted by GORDON STREETER View Post
phoenix, this sounds like a real "seat of your pants" beast to tame, but I bet its not as much of a handful as the Auto Union type C was with oversteer
I think it will be far easier to tame due to the live axle instead of the Auto Union with is swing-arm rear end.
phoenix is offline  
Quote
Old 28 Jul 2009, 21:37 (Ref:2510240)   #10
Andrew Mitchell
Rookie
 
Join Date: Jul 2009
Posts: 18
Andrew Mitchell should be qualifying in the top 10 on the grid
The front is 1 degree toe in and rear is 6 minutes toe in ,thrust angle is 2 minutesallest thats acording to my local mot stations fancy wheel alignment computer.With me in the car the front corner weights ad up to 440 kg and the rear 500 kg .I put the larger anti roll bar on the front and it seems better on the road,i'm hoping to get a test day at castle coombe later in the week ,the car always seems to oversteer more on the track than the road so i'm sure it won't be enough but fingers crossed .For some reason the car seemed softer and more supple around corners but not confident inspiring on the straights as before which seems od to me ,with the larger bar.what do you think?
Andrew Mitchell is offline  
Quote
Old 28 Jul 2009, 21:47 (Ref:2510254)   #11
Andrew Mitchell
Rookie
 
Join Date: Jul 2009
Posts: 18
Andrew Mitchell should be qualifying in the top 10 on the grid
the weights include the driver.
Andrew Mitchell is offline  
Quote
Old 28 Jul 2009, 23:16 (Ref:2510313)   #12
GORDON STREETER
Veteran
 
GORDON STREETER's Avatar
 
Join Date: Nov 2006
Spain
Kent+Mojacar Spain, but not always ?
Posts: 9,400
GORDON STREETER is going for a new world record!GORDON STREETER is going for a new world record!GORDON STREETER is going for a new world record!GORDON STREETER is going for a new world record!GORDON STREETER is going for a new world record!GORDON STREETER is going for a new world record!GORDON STREETER is going for a new world record!
We'll await you're test. Driving a car on the road isn't a true test as you can't throw it about as you do (or should do) on the track. Also heavily sprung and damped cars aren't the best to drive on the roads (especially British ones !)
GORDON STREETER is online now  
__________________
Balls of steel (knob of butter) They're Asking For Larkins. ( Proper beer) not you're Eurofizz crap. Hace más calor en España. Me han conocido a hablar un montón cojones! Send any cheques and cash to PO box 1 Lagos Nigeria Africa !
Quote
Old 29 Jul 2009, 07:50 (Ref:2510509)   #13
Al Weyman
Veteran
 
Al Weyman's Avatar
 
Join Date: Aug 2004
England
South of Watford (just)
Posts: 14,699
Al Weyman has a real shot at the podium!Al Weyman has a real shot at the podium!Al Weyman has a real shot at the podium!Al Weyman has a real shot at the podium!
Have you tried ditching the rear anti roll bar altogether. I have had a lot of trouble getting my old Camaro handling properly since I joined a race series that required me to raise the suspension to give 4" ground clearance. I was suffering with serious terminal understeer and in an effort to cure it went up to a 1 1/8" rear anti roll bar to try to get some oversteer induced. Bad move as I went too far and terminal oversteer was the result, the car was almost dangerous culminating in a crash in wet conditions on the qually warm up lap when I gave it a tad of throttle and it just snapped around something it also done before in front of the whole field at the start but I was lucky that time, not the last time though.

So I did some serious rethinking on the front suspension as I had been up and down through the tyre pressures and it made little difference infact just changed where in the race the car peaked, i.e. low presures better at the end of the race high perssures better at the start! I worked to get the angles better through the suspension curve on the front you can even see the difference from track side photos with the car cornering hard, I then threw away the big anti roll bar at the back and stuck a thin little thing from a standard road car and I have say the difference at Lydden last Saturday was absolutely phenomenal. The back will step out with a bit of throttle (I like that) but it is completely controllable, if it starts going too far just get out the gas and she will straighten up, a real joy to drive now.

BTW is the Bristol engine you are using the BMW derived unit that went into the AC Ace? If so I completely rebuilt one of those once when I was working at Roger Nathans, fantasic old design as I recollect with hemi heads and cross over pushrods.

BTW below is a shot of the car stranded at the chicane at Thruxton as a result of the oversteer situation. :-(

Al Weyman is offline  
__________________
You can't polish a turd but you sure can sprinkle it with glitter!
Quote
Old 29 Jul 2009, 15:10 (Ref:2510831)   #14
phoenix
Veteran
 
phoenix's Avatar
 
Join Date: Jul 2005
European Union
Posts: 1,981
phoenix should be qualifying in the top 5 on the gridphoenix should be qualifying in the top 5 on the grid
Quote:
Originally Posted by Andrew Mitchell View Post
The front is 1 degree toe in and rear is 6 minutes toe in ,thrust angle is 2 minutesallest thats acording to my local mot stations fancy wheel alignment computer.With me in the car the front corner weights ad up to 440 kg and the rear 500 kg .I put the larger anti roll bar on the front and it seems better on the road,i'm hoping to get a test day at castle coombe later in the week ,the car always seems to oversteer more on the track than the road so i'm sure it won't be enough but fingers crossed .For some reason the car seemed softer and more supple around corners but not confident inspiring on the straights as before which seems od to me ,with the larger bar.what do you think?
So, if the car is 940kg it is about 25% lighter than the original car, if you are using the original spring rates, the wheel rates will be about 25% higher overall. However - this is the big one - how much weight has come off each axle when you re-built the car? I suspect, from the handling issues, that more has come off the rear axle than the front.

The front bar may effect a cure, but if the rear springs are too hard (or the front spring too soft as you are now racing the car) IMHO it would be useful to get the front/rear spring rates in balance and then fine tune with the ARB.
phoenix is offline  
Quote
Old 29 Jul 2009, 17:28 (Ref:2510934)   #15
Al Weyman
Veteran
 
Al Weyman's Avatar
 
Join Date: Aug 2004
England
South of Watford (just)
Posts: 14,699
Al Weyman has a real shot at the podium!Al Weyman has a real shot at the podium!Al Weyman has a real shot at the podium!Al Weyman has a real shot at the podium!
I agree you don't want to be too hard on the rear (oh missus).
Al Weyman is offline  
__________________
You can't polish a turd but you sure can sprinkle it with glitter!
Quote
Old 1 Aug 2009, 19:49 (Ref:2513409)   #16
Andrew Mitchell
Rookie
 
Join Date: Jul 2009
Posts: 18
Andrew Mitchell should be qualifying in the top 10 on the grid
The car is much better after the roll bar mod and is going around castle coombe in the 1 28's I don't know how that is for a 1951 2litre? It is still slightly oversteery , but quite well balanced .the tyre pressures are 32psi . what I can't understandis the tyres are getting 10 deg c on the insides and wearing much worse on the insides, because the front has 1 deg - camber I can udderstand that ,but the rear is all square I don't get that,any ideas?
Andrew Mitchell is offline  
Quote
Old 1 Aug 2009, 19:54 (Ref:2513412)   #17
phoenix
Veteran
 
phoenix's Avatar
 
Join Date: Jul 2005
European Union
Posts: 1,981
phoenix should be qualifying in the top 5 on the gridphoenix should be qualifying in the top 5 on the grid
Quote:
Originally Posted by Andrew Mitchell View Post
The car is much better after the roll bar mod and is going around castle coombe in the 1 28's I don't know how that is for a 1951 2litre? It is still slightly oversteery , but quite well balanced .the tyre pressures are 32psi . what I can't understandis the tyres are getting 10 deg c on the insides and wearing much worse on the insides, because the front has 1 deg - camber I can udderstand that ,but the rear is all square I don't get that,any ideas?
Sorry, but could you try that again?

"getting 10 deg c on the inside" means nothing useful to me.

Tyre temps at three points across the tread - outside, middle, inside - both front and rear - would be some useful information that could be interpreted and enable some meaningful response to your question.

It's a long time since I ran crossplies, but from memory you should be in the low 20's even high teens in terms of psi inflation pressure. Mind you, I don't know these specific tyres, so would anyone who knows them care to comment? The wear pattern would certainly suggest to me that the inflation pressure is way too high, given the static negative camber setting. I have a feeling that if you get the tyre pressures and temps right you will be you will be in the 1 minute 25s.
phoenix is offline  
Quote
Old 2 Aug 2009, 11:02 (Ref:2513828)   #18
Andrew Mitchell
Rookie
 
Join Date: Jul 2009
Posts: 18
Andrew Mitchell should be qualifying in the top 10 on the grid
sorry I meant 10 degrees hotter on the inside, i took some imo's to I'll look them out and get them across to you later.
Andrew Mitchell is offline  
Quote
Old 2 Aug 2009, 13:15 (Ref:2513944)   #19
Andrew Mitchell
Rookie
 
Join Date: Jul 2009
Posts: 18
Andrew Mitchell should be qualifying in the top 10 on the grid
The front imo is 67 62 55 and the rear imo is71 73 55 this is at 32psi.Because the tyres are 80% profiles if I go any lower I am worried where the walls are so tall I end up with a lot of side diflection . To me the imo's looked like the rear pressures were a bit high compared to the front,so I lowered the rears to 30 this gave me too much oversteer at first I needed a hand full of opposite lock to get around quarry,which I know is a bit of a funny corner.but when the tyres were warmed up 2nd lap onwards the balance seemed better than with 32 allround, this approach seems good but worries me the car might swap ends on the first corner of a race and end up wiping out half the field. The problem is I am not very experienced with interperating imo data so what do you think?
Andrew Mitchell is offline  
Quote
Old 2 Aug 2009, 14:28 (Ref:2513989)   #20
phoenix
Veteran
 
phoenix's Avatar
 
Join Date: Jul 2005
European Union
Posts: 1,981
phoenix should be qualifying in the top 5 on the gridphoenix should be qualifying in the top 5 on the grid
Hi

From the temperatures I'd say the fronts aren't working hard enough, so more bar needed or maybe stffen up the front spring too.

I found this useful information about 60s crossplies - no guarantees its is accurate, but it does make sense.

Seems I was completely wrong about tyre pressures! Have a read:

Tyre pressure

One of the most significant differences between modern slick tyres and treaded cross ply tyres of the Sixties, is the tyre pressure.
Those tyres needed much higher pressure than anything you’re used to.
The soft sidewalls were easy to bend and create a sloppy and slippery feeling while driving,
and the rolling resistance was quite high, thus lowering top speed and acceleration.
High pressures kept the sidewalls from bending making the handling more precise and would give higher top speed and acceleration.
Furthermore the higher pressure would dissipate better the heat generated by the tyres.
Start from the default setup tyre pressure and work in the range of 30psi (275kPa) for very light
cars and up to 55psi (380kPa) for heavier cars, always cold pressures.
After a couple of laps the IMO (Inside Mid Outside) temperatures should help you understand if you need to inflate or deflate the tyres.
If the mid temperature is higher than the other two, then deflate and vice versa.
Nevertheless keep in mind that most of those tyres are very thin, so it’s normal that
the mid temperature will get higher as the temperature raises.
Another important variable to keep in mind is that a higher pressure makes for a stiffer ride, meaning more precision and agility, but also harsh ride and handling problems over bumps and kerbs.



Tyre temperature

Due to their chemical properties and construction, tyres operate best at a very specific temperature.
Modern tyres once again, have been highly optimized and work in a very limited range of temperatures while at the same time offer various compounds for different ambient and track temperatures.
Once again, this is not the case with the Sixties era tyres.
Their optimum temperature is around 85°C (185°F) but not having multiple compounds on offer - similarly to road legal tyres – their operating range is much more vast, ranging from as low as 50°C (122°F) degrees, before noticing any considerable loss in grip, and up to 110°C (230°F) degrees, again before any noticeable degradation of grip levels.
Keep in mind though that although still sticky enough, operating above or below the optimum temperature will result in more wear of the tyre.
Higher tyre pressure can help lower tyre overheating, and lower tyre pressure can raise the tyre temperatures if they are too low ... do not expect miracles though.
phoenix is offline  
Quote
Old 2 Aug 2009, 14:29 (Ref:2513990)   #21
Al Weyman
Veteran
 
Al Weyman's Avatar
 
Join Date: Aug 2004
England
South of Watford (just)
Posts: 14,699
Al Weyman has a real shot at the podium!Al Weyman has a real shot at the podium!Al Weyman has a real shot at the podium!Al Weyman has a real shot at the podium!
Personally I think you are better having the pressures such that they work better in the early part of the race or you could try filling them with nitrogen to stop the pressure rise something I have never done but I understand Kwik Fit will even do them now for a pound a pop.
Al Weyman is offline  
__________________
You can't polish a turd but you sure can sprinkle it with glitter!
Quote
Old 2 Aug 2009, 15:15 (Ref:2514010)   #22
phoenix
Veteran
 
phoenix's Avatar
 
Join Date: Jul 2005
European Union
Posts: 1,981
phoenix should be qualifying in the top 5 on the gridphoenix should be qualifying in the top 5 on the grid
Quote:
Originally Posted by Andrew Mitchell View Post
The front imo is 67 62 55 and the rear imo is71 73 55 this is at 32psi.Because the tyres are 80% profiles if I go any lower I am worried where the walls are so tall I end up with a lot of side diflection . To me the imo's looked like the rear pressures were a bit high compared to the front,so I lowered the rears to 30 this gave me too much oversteer at first I needed a hand full of opposite lock to get around quarry,which I know is a bit of a funny corner.but when the tyres were warmed up 2nd lap onwards the balance seemed better than with 32 allround, this approach seems good but worries me the car might swap ends on the first corner of a race and end up wiping out half the field. The problem is I am not very experienced with interperating imo data so what do you think?
As for camber, though the front temperature gradient is very good, I would say you might gain a little more front end grip if you take a little negative camber out of the fronts - try adding 1/2 a degree positive. If it works, you can then use this extra front grip capability by loading the front more in roll, with a stiffer front spring or more front ARB, thus taking some load off the rear tyres. Even stiffening up the bump setting on the front shocks might help. Reducing the front toe in to 1/2 a degree or even parallel will again soften the turn in and so maybe help keep the rear end stuck to the track. Just thought - is it possible that the axle is not located too well, and that toe could change by the axle swiveling (in plan view) giving toe out on the outside wheel in a corner? This would give the temperature and wear problems you've noticed - and rear wheel steering!

The rear temps indicate that you have some negative camber on that axle too, but if it is a live axle that is unlikely unless it has been bent at some time - either accidently or deliberately. The outside temperature is very cool compared with the inner and middle - 18 degrees between the middle and outer is huge. It seems likely that only 2/3rds to 3/4s of the rear tyres are working for you. That's a waste of grip which needs to be harnessed if you can find a way. It may be that only lower tyre pressures will achieve that, though it seems the wrong direction to go. You might check the toe again on the rear; the inner temps being high relative to the outside temps, plus the rear end being so lively, both suggest you may have some toe out at the rear. If the toe is good maybe you could add a little more rear toe in, and then reduce rear rebound damping as this should help the rear end stick on turn in.

I think you've got some more testing to do!

Did you make a note of the hot pressures? After you started 32ps front and 30 rear? It would be useful to know the pressure gained on each wheel.
phoenix is offline  
Quote
Old 2 Aug 2009, 15:42 (Ref:2514015)   #23
phoenix
Veteran
 
phoenix's Avatar
 
Join Date: Jul 2005
European Union
Posts: 1,981
phoenix should be qualifying in the top 5 on the gridphoenix should be qualifying in the top 5 on the grid
Just a thought, but the rear tyre temps do indicate toe out. But maybe the toe out is only happening in roll, which would also give rear end steer leading to the uncomfortable over-steery feeling that you describe.

Is it possible that the links that locate the rear axle could be allowing the rear axle to 'swing' in this way - maybe as a result of lowering the car, for example? Any trailing links should be roughly parallel to the ground at static ride height. If they are inclined down from the body to the axle then the axle would be pushed back as the suspension compressed, so giving rise to toe out. This would be more exagerated if the trailing links are particularly short.
phoenix is offline  
Quote
Old 2 Aug 2009, 17:20 (Ref:2514074)   #24
Andrew Mitchell
Rookie
 
Join Date: Jul 2009
Posts: 18
Andrew Mitchell should be qualifying in the top 10 on the grid
The tyre pressures rise 6psi on the outside track side and 4psi on the inside track side.I've got a mate to jack up one side of the car and eyed down the rear wheel to the front one on the other side (not a very scientific approach) and I recon it goes toe out. The rear suspension is the same as a bristol 406 with torsion bars locating under the axle 5 inches in from the wheels ,the rotation of the axle is stoped by one dog bone 18 inches long located above the prop quite far back ,and there is a watts linkage centre back of diff. The 406 was an epic handling car really nimble down leafy lanes, and my car is too on the road this rear wheel steer is good on the road if this what is happening,but perhaps not as good on the track ,the thing is who to limit it ,limit roll which activates it ,or to work with it to some advantage. What was noticable was I started with 6 gallons of fuel in my under fuel tanks and as I was getting down to nothing I could not improve my lap time,making the low fuel tanks were limiting roll when full. I will try to look for a web site with a picture of the 406 suspension.
Andrew Mitchell is offline  
Quote
Old 2 Aug 2009, 17:34 (Ref:2514080)   #25
phoenix
Veteran
 
phoenix's Avatar
 
Join Date: Jul 2005
European Union
Posts: 1,981
phoenix should be qualifying in the top 5 on the gridphoenix should be qualifying in the top 5 on the grid
Quote:
Originally Posted by Andrew Mitchell View Post
I will try to look for a web site with a picture of the 406 suspension.
I've been searching all day - good luck!

It would certainly be interesting to see a diagram as I can't work it out in my head. If their are no pics, could you take some photographs, or even do a sketch?
phoenix is offline  
Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
tyre pressures vs tyre temps ozracer Racing Technology 19 18 Nov 2016 12:06
Tyre Pressures Ilikeearlgrey Racing Technology 18 27 May 2005 18:29
Tyre Pressures Pug620 Racing Technology 14 8 Feb 2005 19:47
tyre pressures laser2 Racing Technology 9 20 Aug 2003 12:29


All times are GMT. The time now is 20:33.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Original Website Copyright © 1998-2003 Craig Antil. All Rights Reserved.
Ten-Tenths Motorsport Forums Copyright © 2004-2021 Royalridge Computing. All Rights Reserved.
Ten-Tenths Motorsport Forums Copyright © 2021-2022 Grant MacDonald. All Rights Reserved.