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Hi all. I'm not a suspension guru like some others but understand most of it. I have always read that less than 2" scrub radius is desired but what about brians protouring better which has to have a large scrub radius. I am trying to design my setup which will be using c5 front and rear suspension. I absolutely love the look of the deep dish wheels. Where do you draw the line on scrub and or track width? Any input is appreciated!
If you're not a "suspension guru", how do you think you can "design" a suspension?
Modern cars have zero to slightly negative scrub radius. Large scrub radii cause hard steering and pull with uneven braking - either due to the brakes or road surfaces. They should be avoided.
You can gain a basic understanding of suspension design by reading Fred Puhn's "How to Make your Car Handle". It's old, but the basics haven't changed.
If you really want to design suspensions, Milliken's "Race Car Vehicle Dynamics" is The Bible.
If you're not a "suspension guru", how do you think you can "design" a suspension.
Modern cars have zero to slightly negative scrub radius. Large scrub radii cause hard steering and pull with uneven braking - either due to the brakes or road surfaces. They should be avoided.
You can gain a basic understanding of suspension design by reading Fred Puhn's "How to Make your Car Handle". It's old, but the basics haven't changed.
If you really want to design suspensions, Milliken's "Race Car Vehicle Dynamics" is The Bible.
Duke
I understand a lot of it and I'm a good fabricator. I don't plan on reinventing the wheel with suspension. I have all the x,y,z suspension coordinates for a c5 and plan to use them. I know the stock c5 has .36 front scrub but when you look at brians vette the wheels and tires go against all the principles that I'm aware of but his vette is extremely fast. I don't plan on competing with my vette but would like the ability to "play" at the track when finished. I was hoping someone could enlighten me that's all.
If it is C5 suspension, then your suspension and tuning is C5 forum material! The wider you go on you rims and rubber, you simply have to have the adjustability to maximize the footprint and naturally you will have scrub. You are looking for adhesion for the speed in consideration of the turn. Sometimes wider tires isn't faster in autocross!
Maybe I am old fashioned, but I always think of guys discussing scrub as guys worried about tire life/mileage! Guys that talk out grip or adhesion or where the tire is contacting the road as performance minded thinking. I still think you try to set your rim offsets for center of tire line, but due to restrictions of sizing under our cars, that could shift that axis and you end up somewhere off center which is your scrub. I like to take temps across the entire tire and attempt to get them as equal across as possible. With adjustability, you can tune in a fraction more at a time with testing for that in combination with great care with tire inflation. ETC.
Our family was the first C3 generation car to fit 335/35- 17 sizings in the autocross world. No one liked us, when we showed up with that rubber! We were out to about a 78" track back in the day. I don't remember if that was in 1987 or 1988. The 1987 F40 Ferrari came out with those and we thought, what the heck and did it, with some cheap custom made NASCAR level steel rims, because of the C4 cars that were starting to populate the ranks, we decided to dramatically upstage those new models!
Last edited by TCracingCA; 11-28-2015 at 01:26 PM.
In this picture from that era, it is wearing the less aggressively wide street tires, but this picture will give you can idea of what sizes of rubber we were fitting with our homemade flat style flares (about 27" diameter was our limit, but we were unlimited on this car as to ultimate width within reason and on a C2/C3 suspension!)!
Last edited by TCracingCA; 11-29-2015 at 08:29 PM.
We have had to prove that constantly many times! And if someone pulls up alongside missing the clue, they usually are in trouble! That was with drag race rubber, but solid 3 sec range on the pavement. The road race suspension with the heavy springs helps the launch greatly!
In about 1989-1991? (we got the BFG newsletter and immediately bought the first autocross rubber), we dropped back to a 315/35-17 because you could get dedicated autocross rubber in that size instead of shaving tread blocks on ours and they were cheaper than the limited car model equipped 335s. That size (315) was also standard equipment finally on the ZR-1 Corvettes from 1990.
Last edited by TCracingCA; 11-29-2015 at 08:32 PM.
So I will take a moment more! These car suspensions are designed for certain sized tires and rims. Adding big tires and rims changes that, and you generally can't change your a-arms. So if you are designing your own components, there is a chance of correcting this scrub (steering offset)!
And lastly, I have hit the weight room during the entire Ownership of big tired cars, especially in consideration of no power steering! But I know the modern enthusiast expects one figure touch power steering, from the comfort of something very sofa like and then they think that they are great drivers!
Last edited by TCracingCA; 11-29-2015 at 09:07 PM.
Thanks everyone for your input. I ended up talking to Ron Sutton who is a suspension guru to say the least. He's going to help me dial in the front suspension. I'm probably still going to run 1-2" of scrub on the front because I like the look of a little lip on the rim but that's just my opinion. I know the ideal setup is I just am waying looks vrs performance.
11-25-2015, 08:16 PM
Tire scrub radius importance vrs track width
