Why Do Rally Cars Run Small Wheels?

kanaric wrote: This car always seemed to have quite large wheels for a rally car and it's one of the most successful ones.

Note that car is on a tarmac setup.

Some of the Group B cars ran 16" gravels (some of the Audis did) but somewhere in the Group A era they mandated some strict size limits, no more than a certain width, no more than 65cm in height, and I'd like to say that was when wheels were limited to 15" for gravel.

It's just not practical for a niche market to make more sizes of gravel tires. There are some rules limits depending where you are in the world and that limits some world wide production.

GRC tires are one standard size spec tire for both the lites and supercars, likely to reduce production requirements. Happens to be the same as the world rallycross size. Also happens to be a very popular diameter of 17. There is a fine line between ideal traction, and air pressure needed to resist debeading in a side impact.

captdownshift wrote: In reply to kanaric: the subaru guys retrofit on 4 pot calipers to run 15" wheel and tire packages

Yup - 4pot/2pot brakes from USDM 06-07 WRX models or aftermarket brakes that will fit under a 15" rim.

¯\_(ツ)_/¯ wrote: In reply to NickyDaFish: What are you trying to do? RallyX vs. Stage Rally vs. just for looks? Irish44j and I run stock wheels because they're cheap and therefore disposable, and sometimes stock wheels from other cars can give you a lot of good options depending on your bolt pattern- I use stock Saab wheels on my Merkur for example.

Rallycross in a 2001 BMW 325xi, there are 15in BMW wheels I can find on CL for cheap and should fit. Tossed up with running 16's with winter tires or 15's with proper rally tires. I race with Susquehanna SCCA and Blue Mountain Region SCCA so surface varies from loose dirt to gravel to the frozen tundra we had this past Sunday. I usually race SA but am not classification focused, just want to go fast. Full disclosure, I've read both your's and Irish44j's build threads front to back. Awesome stuff.

captdownshift wrote: In reply to NickyDaFish: Hit up Paul E. with Braid wheels, they aren't cheap, but it's unlikely that they'll ever need replacing. For tires, hit up JX2, ask for Eric Jackson and tell him you need gravel pirellis and that Dave Z from Porsche sent you. Every vendor in North America that sells Pirelli rally rubber gets them from JX2 now the Bob Woodman no longer doesn't pirelli.

Thanks Cap!

In reply to NickyDaFish:

Go digging for my Foxbody RallyX thread if you want to see what NOT to do

Staying in stock with snow tires will be the easiest, but you probably already know that. Sounds like you're near me, which is a little bit of a bummer since I just sold some 15" gravels (I'll probably have more for sale next summer). Gravel tires will make you faster when it's not muddy/snowy/whatever last weekend was, but they're useless otherwise- if I were rallycrossing a car that also gets driven to work I might go with snows just because they're useful when it actually, you know, snows.

It depends on your goals as well- I wish I hadn't spent so much on rallycross, if I could do it again I would stay in stock class and save the money for stage rally. If you're smart enough to not want to move into stage rally, go nuts!

Probably just stay with 16in snows then, just seems too practical to be any fun. I live in Philly which means no garage so car maintenance happens on the street. Not super practical for prepping for stage rally, though I would love to undertake it, maybe at some point down the road. Looks like BMRSCCA will be running events all winter, I'll keep my eyes peeled for the xrati.

NickyDaFish wrote:

irish44j wrote: rally gravel tires have extremely stiff sidewalls - I can put mine flat on the ground loose off the wheel and stand on the inner bead, and it hardly even flexes under my 175lbs. Tire mounters hate rally tires because they often take 100+ psi to seat the bead. I have never debeaded a rally/gravel tire in 5+ years of rally/rallycross (though it does happen). The wheels are small so we can have tall sidewalls. Going sideways into a corner full of 6" rocks, if you have a low profile tire you will end up with a bunch of broken wheels. Taller sidewall takes the impacts. I'd like a taller sidewall, personally (we run 185/60/14), but our little 1.8L and gearing limits us if we actually want acceleration. Rally/gravel tires are HEAVY.

The tire/wheel/drivetrain interplay is starting to make sense now. Any good reccomendations for vendors that sell wheels and tires? Thanks to everyone who has chimed in.

I order all my tires from the UK. www.demontweeks.com. The tires area like half the price as in the US. Even with shipping it ends up a couple hundred bucks cheaper for a set than at anyplace in the US.

Alternately, if you just want them for rallycross, go buy used ones off a rally team. The top teams sell them after each rally, usually with like 75% of tread still good. That's how I got my first several sets used. Get on the rally facebook pages and you'll constantly see them for sale.

¯\_(ツ)_/¯ wrote: In reply to NickyDaFish: What are you trying to do? RallyX vs. Stage Rally vs. just for looks? Irish44j and I run stock wheels because they're cheap and therefore disposable, and sometimes stock wheels from other cars can give you a lot of good options depending on your bolt pattern- I use stock Saab wheels on my Merkur for example.

As Chris said, we just use stock wheels. I mean, I'd love some Braids, but I have 3-4 sets of wheels wiht different tires (soft compound, medium compound, worn-down ones for rallycross, snow tires, etc). I think all those stock wheels costs me about $200 total, lol....about what one Braid costs. Plus, they're basically disposable. Hit some train tracks...whatever...toss em in a dumpster on the way home. For rallycross, there is definitely no need for high-end rally wheels. For stage.....if you're a fast-mover/top car with a good budget - go for it for sure. But a good chunk of the regional rallyists just use OEM wheels from whatever cars fit theirs (in my case, there's no shortage of e30 bottlecaps always availabe).

kanaric wrote: This car always seemed to have quite large wheels for a rally car and it's one of the most successful ones.

plus that setup is for tarmac rally, a different story. The Deltas running off-road rally put on taller-sidewall tires...and IIRC also used smaller wheels (though they looked the same style-wise)

Little to add here other than those are some sexy rally car shots...

¯\_(ツ)_/¯ wrote: In reply to NickyDaFish: I wish I hadn't spent so much on rallycross, if I could do it again I would have just bought one decent, known-quantity car and modded it appropriately rather than buying four different oddball vehicles that were either unreliable or uncontrollable..

Fixed for you, Chris

In reply to irish44j:

Don't forget slow (Celica)

I still wouldn't bother with an MR class build though, and I lack the patience to do what you did with the e30.

In reply to ¯_(ツ)_/¯:

An MR Volvo 240 build wouldn't have drained the wallet too badly and still could be made to be properly bonkers

16" Gravel tires were a necessity for a time for brakes. When brake pad and cooling technology improved it allowed them to go back down to 15" for gravel tires.