RALLYCROSS: help with 17"wheel/tire selection for GR Corolla

I bought a GR Corolla last January, planning to have some non-street fun with it. Kinda waiting to have some miles on it, now has about 3K miles, so should be good to go for next year.

I have RE71RS on the stock 18" wheels for autox and possibly track. (I'm an old guy, used to do both a lot, but not for about 20 years or so...)

I have DWS06+ on 18" silver Enkei TS-10 for street use.

I loved rallycross many years ago (actually, that was before it was even called rallycross lol) in a 323GTX hopped up with HKS stuff to keep up with the Eclipse and Talons. Lotsa fun. (A "dirt autocross" was newsworthy 30 years ago- won annual KY event 3 years in a row- covered in both GRM and SportsCar, see below.)

Anyway, the GR is pretty low, but Eibach just introduced GR springs in low, lower, and raised spec. I bought a set of the taller springs, which will lift the car an inch or so.

https://eibach.com/product-releases/2023-2024-toyota-gr-corolla

Which I know also moves me out of stock class. I doubt I'll be competitive with fully-prepped Subies, but that's ok. Objective is to have fun.

It's tight, but some 17" wheels fit over the big front brakes.

Some questions:

1) How bad would it be to just start with the 18" DWS?

2) If I go to 17, snow tire or rally tire?

3) Size? I think increasing tire diameter an inch should fit ok. That would include 215-55-17 and 225-50-17

4) What's best for keeping the tire seated on the bead? Narrowest wheel? For example, 17x7 better than 17x8?

5) Do you want soft sidewalls for more compliance for bumps, or stiff sidewalls (runflats if available?) for resistance to debeading? (Is that the right term for the tire unsealing and flattening in a millisecond? Had that happen once on my 323GTX with 14" wheels!)

6) Any other thoughts/suggestions/comments?

Thanks!

.

Welcome to GRM. 

I'm in the same place you are - wondering what size wheels and tires to use for a set specifically for rallyX.

A lot depends on the course surface and conditions. For "traditional" soft surfaces you realistically want the narrowest, tallest tire you can fit. 17s are nice for the extra sidewall height, I'd be wary of running wheels with super low brake clearance though because dirt, rocks, etc are going to get up in there and could do some real damage. For harder/packed surfaces anything from all seasons to autocross tires could work. I don't think anyone makes runflat versions of appropriate snow tires but I could be wrong. In general there's very few situations where rally tires are genuinely faster than snow tires in outright pace. Now, once you factor debead prevention into that things might be a bit different. The vast majority of my experience is with RWD, so I don't know much about that. The all seasons might be fine, again depending on the surface and conditions. In any case I'd start with either those or some snow tires and see how things go before committing to the expense of rally tires. Also I think the options for 17" rally tires are few if any so you might not have much of a choice and be basically limited to snow tires anyway.

Paul,

A lot of the answers really depends on the surface your local region races on and how rough the venue may be.  Here's my best estimates without knowing all the details.

1.) They would probably be fine, though not the most competitive tire, on most surfaces.  The sidewall is a little short, which risks wheel damage and likely increases the chance of debead (less surface area for the air pressure to push against)

2.) Tire choice is HIGHLY dependent on the surface.  My region (Iowa) has six venues currently and drastically different tires are needed depending on the venue.  At our dirt tracks, the fastest tire is typically a 200 TW tire, like the RE71s mentioned.  A sticky all-season is typically quite fast as well. Our farm field venues typically need a tire that will move as much material as possible, but you don't want something with hard rubber as you're giving up friction grip.  With you being constrained to 17" wheels, you can't get any of the really good rallycross specific tires, which are only available in 15".  The only rally/rallycross tire design available in 17" is this one.  Several manufacturers offer a tire in essentially this same pattern and size; most are a rallycross tire without the major sidewall reinforcement of a true rally tire.  They are okay for very loose surface venues.  I would go with a soft compound to get more grip, but I'm also willing to buy tires more frequently then some.

There's some decent snow tires available and on some surfaces, they may end up being faster than the rallycross tire above.

3.) More sidewall is typically a better thing, as it give more area for the air pressure to hold the tire on the bead.  In addition, it allows for more tire flex, putting more rubber on the ground.  I've heard other opinions on this topic, but in my experience, more sidewall is better.  Narrow tires are better for loose surfaces.  You may give up a small amount og cornering grip, but it will be more than made up for with the longer contact patch when you're trying to accelerate.

4.) I am a big proponent for narrower wheels.  I'm running 15x6 wheels with my tires ranging from 185 to 205 width.  I have witnessed the exact sime tires debeading repeatedly on 7" wide wheels, on a lighter car, with more air pressure in them.

5.) There's two schools of thought on this, but as I mentioned previously, I tend to like more compliance.  In addition, most if not all of th run flat snow tires are fairly low profile sidewalls.  Debeading is the correct term.

6.) Like anything, the more serious you are about things, the more sets of wheels and tires you are going to find yourself owning.  I have more sets of tires than I like to admit and have more on the way for trial purposes.  You are likely going to have to do some trial and error stuff to see what works well on that car, since few have traveled the rallycross road yet.  You may want to chat with some of the guys that have championed Focus RS's in SA at Nationals as the tire sizes they used is likely similar to what you'll end up with.

Nothing to add other than I miss my silver 993!

Please keep us along for the ride as you use your GR as intended!

 Guys, thanks very much for the thoughts, many very helpful ideas.

dyintorace said:

Nothing to add other than I miss my silver 993!

I sold my second 993 in 2020 and immediately regretted it. A year later I told the guy if he ever decided to sell it, he should let me know. 

Last spring he emailed me, saying he was going to sell it, and quoting a price that was 1/3 more than I had sold it to him for, but still was very fair in the 2023 market.

After about a millisecond I told him, "I'll take it." Then a few days later rented a car here in Cincinnati, drove to Hickory, and brought it back home.

https://rennlist.com/forums/993-forum/1347042-sold-my-993-in-2020-regretted-that-just-bought-it-back.html

Just read the whole thread. Great story! My 1996 was a C2, Polar silver over Flamenco red (full leather). I miss it but not enough to chase it down and pay current prices for it!

dyintorace said:

Just read the whole thread. Great story! My 1996 was a C2, Polar silver over Flamenco red (full leather). I miss it but not enough to chase it down and pay current prices for it!

I personally love the way the 964 and 993 straddle the line between vintage and modern cars, but most passengers just say, "It's kinda tight and noisy in here."

After talking to BraidUSA.com, I ordered 17x7 ET30 Fullrace A wheels. (They can do other sizes and offsets, too.)

https://braidusa.com/collections/autocross/products/fullrace-a-wheels2021-june?variant=40182791569563

I added custom color, centercaps (not sure why), and their "Beadlock B" system, which is different from the clamping-style beadlock system used by offroaders who run very low pressure. But Braid says this is a very good system for rally/rallycross.

https://cdn.shopify.com/s/files/1/2550/9890/files/BRAID_Beadlock_B_System_instructions.pdf?v=1599064191

All wheels are made to order. But since I'm not in a hurry, I saved on shipping by waiting until their next container was coming.

Still considering whether to get 215/55-17 snow tires or the 225/50-17 Alpha rallycross tires.

*note: since you posted this question also on the Washington DC rallycross FB page, I assume you're planning to run with DC. If not, you can kind of ignore most of what I'm about to say*

Anyhow - the guy that answered your question in the FB thread (Adam K.) is one of the fastest AWD rallycrossers in the country (and also has won a bunch of stage rallies). So his advice as it pertains to DC region courses (or pretty much anything rally-related) is likely the best you'll get. Our surfaces and courses are NOT like most other rallycross venues in the US, so the advice you'll read in a lot of places doesn't apply. 

A lot of the folks on GRM don't run with DC, they run on grassy/loam fields. We run on hardpack clay and gravel, and have higher-speed courses. IIRC the Alphas are grass tires, which will wear down FAST on our courses and also won't be all that good. 

As Adam noted - since you can't get real gravel tires with 17" wheels, your best option is to get a performance snow tire (e.g. Dunlop Wintersport M4, Blizzak LM-series), if you're running with DC only. Now, if you run Susquehanna region, they have some grass courses, so the Alphas would be better.  In the summer, at Summit Point, the course gets so baked some people actually switch to stret tires (or tarmac rally tires). 

Also - the snow tires are a lot cheaper....best to use them to start and then decide if you want to drop the cash for the Alphas (IIRC, nobody in DC runs them).  In the end, don't overthink it. Maybe go up +5 on the sidewall (so, 215/45/17 --> 215/50/17 or whatever) to get a bit more sidewall also. 

As to beadlocks, never heard of people using them in rallycross, and almost nobody uses them in stage rally either.  Not to say they don't work, but if you're debeading on a DC course, you're going something wrong, generally. Also, definitely do NOT get runflats. Heavy, no sidewall compliance, etc. 

In reply to irish44j (Forum Supporter) :

I agree with everything except the alpha rallycross tire looks like a gravel tread pattern.  The eurocross everyone uses is the grass tread pattern.  I don't know enough about the alpha compounds to say for certain but mediums or hards in the rallycross pattern should work.

In reply to centerpunch1 :

If you can get a 17" tire X 7 or X 8 then you can try these, 

https://www.alpha-racingtyres.com/products/rallycross-225-50-r17-medium

He ended up with these.  Then I bought the car in July.