Just wanted to post this as a fun little “food for thought” idea. Here’s my situation. When I bought my M3 it had old, bald, mismatched tires so obviously they have to go. My plans are to run a wide 18x10.5 square setup with overfenders. I just got my Apex arc 8’s in this week. Between the wheels and numerous maintenance/refresh parts I’ve been buying, I needed to cut back on the spending so I bought some 275/40/18 Achilles atr sport 2’s for my wheels. These are just temporary rollers so I can fit my overfenders and get rolling. I’m sure I will run through these tires way before my car is dialed in to how I want it so it got me thinking..
What setup would provide better traction?
An oem sized 245/40/17 rear tire on Michelin Pilot Sport 4S’s on an 8.5j
or
much wider 275/40/18 Achilles on a 18x10.5?
My car is maybe 30 hp over stock so I’m definitely not overpowering the tires at this point.
I’m drawing inspiration from Terry Fair and Jakermac with their wide tired, lightened and not overly powered cars so that’s the direction I’ll be building my car as time and budget allows.
I've run square 225 BF Goodrich G force rivals in mine and stock 245 rear with 225 front semi sporty Yokahama tires. The narrower G force rivals blow the Yokahamas out of the water. Better rubber compound is worth a lot.
I run the G force rivals in autocross, they very much improve the traction and general control of the car.
I'm at about the same power level as you, honestly, there isn't much difference in dialysis performance, it mostly is felt on the track.
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I have run Achilles tires on my Austin Healey Sprite as they are the only modern tire I can find that fits. They impress me, good grip, just don't wear very long.
I agree with you that a superior rubber compound is irreplaceable but at what width over stock can the traction begin to get close to narrower but superior tires? No need to answer, it’s just something I’m curious about.
Thanks for sharing your experiences on the subject.
Last edited by 21deep; 05-25-2020 at 10:37 PM. Reason: Missed something
Superior compound is definitely superior to wider width. I find overly wide tires to be detrimental for street use- numb steering, poor ride, tramlining, etc.
Last edited by sirhodjibob; 05-25-2020 at 11:09 PM.
I remember thinking about this 20 years ago. Now I run wider than stock good summer performance or R compound tires on wider than stock wheels.
there was a very good thread about this a while ago... but basically, it's all about compound. A wider tire won't necessarily help and could actually impact response and feel negatively, not to mention you may be adding more weight.
TRM Coilovers 670F/895R | BBS LM | Corsa RSC36
I recommend sticking with stock sizes and just getting better compounds for a street car.
At 10.5" wide wheels, you'll introduce a whole set of issues like body modifications (pulling/rolling fenders) and more suspension loads for a benefit that's marginal at best, and especially for a measly 13% power bump over stock
-Rich-
I’m actually building a trackable car, the thing about it is that the track won’t be built until a few years from now so I’m keeping it streetable for now.
I’m going to fit the tires, I’ve done my homework and I know it’s going to take cutting, overfenders, spacers etc. I’m not worried about that. I’ve done those modifications before.
As far as the current power levels, my car is not in its final form. I’m not going to put any more money into my S52 for diminishing returns. I haven’t dynoed it but I estimate it at 275 hp at the crank. I’m still doing my research into motor swaps but I’ll most likely be putting in a k24/k20 because of the power potential to weight and because replacement engine are common and cheap.
A longitudinally-mounted K24/K20 is not such a great idea for a track car. Even with good baffling, they suffer from oiling issues. I don't know if KMiata ever figured out the problems and how to address them on K-swapped Miatas, but I imagine you'd need something like a Accusump
-Rich-
This is a great point about the weight impact.
I had Style 68s - which are the lightest factory wheels available. I got ARC-8s, which were about 5lbs per corner lighter, and it made a dramatic difference in acceleration.
Handling too, but they were wider and had a lower offset, so that's not a fair comparison when it widened the car 3.5 inches.
So it kind of depends on what you're looking for out is this. Bigger wheels are far heavier. Cheap tires are usually heavier than the Michelins, too.
You might turn a faster lap with a really wide cheap tire than a good stock size tire, but you might not. For sure it'll be slower from a stop light and around town. Of course, you can always upgrade your wide wheel to a good tire.
So it just depends on what you want out of it.
-Josh: 1998 S54 E36 M3/4/6 with most of the easy stuff and most of the hard stuff. At least twice. 271k miles. 1994 E32 740il with nothing but some MPars. 93k miles.
The Achilles tires seem pretty light to me, but that doesn’t necessarily give me comfort being that it is very cheap. Also, the sidewalls flex more than I prefer but I will see how they feel when they are mounted. I don’t actually intend to track these tires though, I’m not sure how much I would trust a cheap tire at speed.
Like most things, it depends. What kind of acceleration? to go forward, you want a long skinner tread patch. to corner, you want a wider shorter patch...
Basically you want the contact patch to be along the direction of acceleration.
Top fuel cars don't turn, and have a narrow, long footprint as soon as the tires start moving.
Road racing cars have wider tires to carry speed in turns.
It's a compromise. But generally, sticky tires win and wear out faster.
No matter where you go, there you are...
Michelin and Continental tend to be among the lightest in high performance summer tires. They could be 10-15% lighter than others. And most stock wheels are heavy. You can save another 10-15% in weight by running wheels like the Apex ARC8. Yes, going wider adds back some weight. Look up the specs and do the math for the options you are considering.
True. Have you considered a proven F20C? I mean, it was originally designed to be a longitudinal mount and that's why the K isn't preferable in such a setup.
It was the first factory-spec street car engine to reach 120bhp/L (I think even counting boosted engines)
Truth, on my E36, I have had Kosei K1s and those were over 6lbs/wheel down over stock. That's over 24lbs of unsprung mass so it's a giant difference!
On my current Civic Si, I dropped over 9lbs/wheel over the heavy stock wheels and it's a beast of a car in handling for the same reason
-Rich-
As a point of reference, maybe not applicable to street, but on our s54 e36 race car (325 rwhp), we typically run 265 pirelli slicks. On our e46 s52 (305 rwhp), we run 245 pirelli slicks. WHen we put the 245s on the e36, we get basically the EXACT same lap times, but they come from different parts on the track ... the 245s are faster top speed (less drag and frontal air probably?), but the 265s corner a tiny bit faster. That event out to same lap times. The 245s FEEL faster because they are much more crisp and precise when it comes to steering input, whereas the 265s are kinda numb feeling, but ultimate lateral grip, they win.
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