Why are rallycross cars so unreliable?

[madcowie2007]

Please dont take this as an offensive question.

Rallycross cars are not that different to rally cars. Obviously there are a few fundamental changes! But rally cars do back to back 20 mile stages and dont break down anything like as often.

Last weekend at Croft it was no different to any other year of the spectacular event. 20 supercars entered and by the end of the weekend 10 were left running. Not to mention all of the other mechanical failures the drivers had but managed to repair.

I know these machines are fine tuned and dont have factory support and run on a low budget compared to other sports. But is this the reason?

Thank you
Madcowie

[chris cake]

Mainly because a rallycross Div 1 car has at least 200 Bhp more than any rally car !
1 This is a massive rise in stress levels on the engine over anything in rallying
2 Huge amount of extra power tests all of the important componants, Gearbox
Diffs and Driveshafts to the max mainly during the start .

The best person on here to tell you more would be The 2007 Rallycross Div1 Open and MSA Supercar preparation champion Mr B !

[chunder]

Chris is clearly on the button here, and also I think a huge problem is the suppliers that rallycrioss people use.

In my ind there are plenty of ares of motrosport with cars more powerful than rallycross, drag racing for example.

there are 1000hp four wheel drive drag cars that only ever accelerate on asphalt, surely the people that supply shafts and stuff that is likely to blow could help.

Anotehr problem I think is contact, these cars are no doubt damned hard to drive on the limit, hence there is often much contact and the parts used are a little hughly strung shall we say, so they break easily.

As Chris says WRC cars have 350hp at the most so most of the parts used are not goona be able to withstand 500+hp and 700 ft-Lbs of torque.

I think Quaife use rallycross to develop new bits aswell as supplying.

[sjones]

If you take a look at Hansens car it's basicly a test mule for next years car. That C4 he's been driving this year has parts which will be seen on the 2008 WRC car. They basicly give him stuff to break because Rallycross is a much more stressful sport on the car to be sure they can sustain the WRC stages.

[Chessmsport]

Originally Posted by sjones

If you take a look at Hansens car it's basicly a test mule for next years car.

Hansens C4 and C4 WRC have nothing in comman they are completly different cars.

[The Eye]

Originally Posted by Chessmsport

Hansens C4 and C4 WRC have nothing in comman they are completly different cars.

They benefit of each others development. Hansen tested out several components for Citroen Sport on the Xsara before they drove it in the WRC. And Hansen off cause have had benefited from Citroen in their tests! They have probably done the same thing with the C4.

[The Eye]

Originally Posted by madcowie2007

Please dont take this as an offensive question.

Rallycross cars are not that different to rally cars. Obviously there are a few fundamental changes! But rally cars do back to back 20 mile stages and dont break down anything like as often.

Last weekend at Croft it was no different to any other year of the spectacular event. 20 supercars entered and by the end of the weekend 10 were left running. Not to mention all of the other mechanical failures the drivers had but managed to repair.

I know these machines are fine tuned and dont have factory support and run on a low budget compared to other sports. But is this the reason?

Thank you
Madcowie

If you take a look at some pictures of a WRC car at tarmac spec and some in more ruff gravel spec you will notice there are quite some differences. The setup for an asphalt race is usually a low and stiff suspension because the surface is smoother than on gravel. On a gravel race you have a softer and higher setup. The road is “bumpier” and you have to have a suspension that “eats” the bumps!
In Rallycross you have to compromise a bit. A Rallycross track is often 60% tarmac and 40% gravel. The start is very important in RC. So to optimise a good start setup you lower and stiff up the suspension. And that is often good for the asphalt parts as well. And sense the start and the 60% tarmac parts are so important rallycrossers tends to drive a rather stiff setup, but on the bumpier gravel sections and when they hit the curbs there are not always enough movement for the drive shafts and that is often the cause of Diff and Driveshaft problems.
And as Chris Cake and Chunder pointed out, 200 extra hp and contact do not make things better do they

[BertMk2]

All of the above are very true - but I also think the reliability of rally cars is being overstated, especially at club level. The drop out rate due to mechanical failures is usually fairly high, I'll dig out some numbers from some of the events I've done (not all drop outs are mechanical obviously but a large percentage are). On the Tempest rally yesterday we passed at least 4 cars stopped in the 1st stage

Retirements on the Tempest:

http://www.tynecomp.co.uk/Results/ot.../2/retire.html
http://www.tynecomp.co.uk/Results/ot.../1/retire.html

[StockHatch782]

Originally Posted by BertMk2

The drop out rate due to mechanical failures is usually fairly high, I'll dig out some numbers from some of the events I've done (not all drop outs are mechanical obviously but a large percentage are). On the Tempest rally yesterday we passed at least 4 cars stopped in the 1st stage

We were watching on the Tempest yesterday, too, and every stage we watched there were less cars coming past. I think it's partly because at a rallycross meeting you can either see the cars retire or see that the grid is a lot smaller, whereas in rallying the cars just don't come past so it's not as obvious they've had mechanical retirement.

Generally, the more exciting a car is to watch the less reliable it is likely to be.

[Cryos]

Originally Posted by chunder

Chris is clearly on the button here, and also I think a huge problem is the suppliers that rallycrioss people use.

In my ind there are plenty of ares of motrosport with cars more powerful than rallycross, drag racing for example.

there are 1000hp four wheel drive drag cars that only ever accelerate on asphalt, surely the people that supply shafts and stuff that is likely to blow could help.

Anotehr problem I think is contact, these cars are no doubt damned hard to drive on the limit, hence there is often much contact and the parts used are a little hughly strung shall we say, so they break easily.

As Chris says WRC cars have 350hp at the most so most of the parts used are not goona be able to withstand 500+hp and 700 ft-Lbs of torque.

I think Quaife use rallycross to develop new bits aswell as supplying.

I would have to agree with you there, ive found that american suppliers tend to have components that last longer and seem to be alot stronger; Afterall look how many boy racers in the states have their supra's, evo's and imprezza's between the 500-800hp mark..

I hear Australia is where you have to go to get the best impreza boxes...

I think its evident, because if you look at some of the top ERxC guys their cars do seem to take the punishment; The likes of Eklund, Hansen, Joranli and schance put out the best gear into their cars, that they have probably hand made themselfs from the best components.

[rx-guru]

The answer to that "apples vs pears comparison" is actually quite simple:

If one would drive a Rally with 95+% effort he would hardly see the finish at all.
If one would drive a RX with 100-% effort he would hardly be among the top finishers.

[BertMk2]

Originally Posted by StockHatch782

We were watching on the Tempest yesterday, too, and every stage we watched there were less cars coming past.

Which stages did you watch? Yateley and Warren seemed to have the most cars stopped in them but we found Ash and Longmoor to be much rougher.

[StockHatch782]

Originally Posted by BertMk2

Which stages did you watch? Yateley and Warren seemed to have the most cars stopped in them but we found Ash and Longmoor to be much rougher.

We watched Yately and Warren, they seemed pretty smooth in most places as far as we could tell but I did hear the other stages were pretty rough. Track-rod ends broken in pot-holes etc.

This is another area where comparing rallycross and rallying is, as rx-guru says, an 'apples and pears comparison' - gravel rallies are generally much harder on suspension etc., tarmac rallies are often harder on transmissions and rallycross is hard on both, but each to a lesser extent.

[BertMk2]

Originally Posted by StockHatch782

We watched Yately and Warren, they seemed pretty smooth in most places as far as we could tell .

They were pretty smooth but had cut up quite a lot by the second run through. We had a small off in Warren on the first run through there but fortunately we had enough momentum to carry us back onto the road

Originally Posted by StockHatch782

but I did hear the other stages were pretty rough. Track-rod ends broken in pot-holes etc.

Some of the potholes in Ash and Longmoor were huge, we got chucked about a bit by one of them in particular - I'm not surprised that cars were breaking through there.

Originally Posted by StockHatch782

This is another area where comparing rallycross and rallying is, as rx-guru says, an 'apples and pears comparison' - gravel rallies are generally much harder on suspension etc., tarmac rallies are often harder on transmissions and rallycross is hard on both, but each to a lesser extent.

It's certainly true - as mentioned above rallycross cars are set up to deal with both surfaces but are compromised as a result. Also the very nature of rallycross means that cars are only required to run in short bursts - so why over engineer them to last longer. A supercar that 'only' ran at 300bhp would more than likely still be running at the end of the day, the chances of winning though would be very slim indeed. So in addition to the setup compromise there's also the power compromise - you need as much as possible to be competitive but after a certain figure on any given engine you know that it's not going to be totally reliable. How far you go is another call you have to make - sometimes it pays off, others it doesn't.

[DCS]

I don't think WRC's are so reliable anymore if they would enter the ERC scene. As all top Rallycross drivers point out the drivetrain would be the fist to give in if it is given the power and agressivenes a ERC engine will offer. One of the reasons why the Hyundai now has a Schanche gearbox and not the WRC transverse Xtrac anymore.

And I am also not so keen if the WRC engines are builld to withstand the extremely high boost used in the ERC especially in the pre 45mm era. I do believe the 45mm restriction will make it more possible for WRC's to enter in that regard.

It is yet to be proven that a modified WRC can win a ERC championship...

[sjones]

A prime example of WRC standard cars in Rallycross is GT's 307. He hasn't had the best of things come out of that car.

[leonidas]

Its also partly a function of rallycross rules and championship scoring.

You don't have to worry about getting to the end of a 16 mile stage if something breaks after a couple of miles. You get towed back to a nice comfortable garage and and hopefully fix it in time for the next heat.

The scoring system means you can drop a scored round (sometimes more than one) - allowing you a free breakdown. Bonus points for ftd also means that speed is favoured over consistency.

My own impression is that the euro restrictors have reduced the number of failures. But maybe engineering has become a bit more conservative too in the midfield ranks? Blowing things up can be expensive!