Track Tac

LR size vs Right sides

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KartRacer89

Member
Hi everyone, I've been on Bobs for a while and there is a ton of good info on here. A friend of mine that's been racing for many years once said to keep the LR at 33 inches and to grow the right sides to get my stagger. I'm not trying to call anyone a liar or start a huge argument, because I'm still a novice and I have a lot to learn, but I've read differently on here.
 
KartRacer89 said:
Hi everyone, I've been on Bobs for a while and there is a ton of good info on here. A friend of mine that's been racing for many years once said to keep the LR at 33 inches and to grow the right sides to get my stagger. I'm not trying to call anyone a liar or start a huge argument, because I'm still a novice and I have a lot to learn, but I've read differently on here.
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This is a to each there own subject, I let the tires of each set tell me where were ending up, but pretty much the LR decides the out come because some you can shrink and they will hold , but more times than not a LR that's 33 " will usually end up just that 33" , then others are 32.75" , then every once in a blue moon you get one 32,5", this is with Burris 33's, we either need 1,25" rear stagger or 1,5", front is always 1.5" , And I'll have LF's from 32" to 33" so whatever my LR's stay consistent at for each different set we make the biggest of the 2 Rights what ever we need for the RR , and the smaller right side we can usually keep at 34" for the RF.
 
KartRacer89 said:
Hi everyone, I've been on Bobs for a while and there is a ton of good info on here. A friend of mine that's been racing for many years once said to keep the LR at 33 inches and to grow the right sides to get my stagger. I'm not trying to call anyone a liar or start a huge argument, because I'm still a novice and I have a lot to learn, but I've read differently on here.
Click to expand...
Most use 33" as really a baseline, it can vary as Race Promoter said.
More often than not your tires blowout at close to the sizing you want, and you may or may not adjust from that point. Reason why we have certain size tires for LF, LR, and the rights.
 
I'll second racing promotor and say I've conceded to sizing around the LR. Ideally I want my LR 32.75" but it can be a pain to size. Most of my Vegas are 32.75" but Maxxis 33".
 
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I'll side with the folks using 34" right sides as often as I can.
While you may not notice much difference from 34"- 34 1/4", it does change how the car works on the track (even if slightly.)
Consider that all the chassis manufacturers build their cars around a 34" right side tire. They go through pain-staking effort to jig, bend, and weld your chassis to exact ride heights - that's not by accident.
I want my race program (and my customers') to have as consistent baseline set-up as we can get, and that always starts with 34" right side tires.
We size tires nearly every day in our shop (as do most every other tire guy, chassis mfg'er, and racer.)
Sometimes sizing tires takes more effort than others - that's all part of the deal.
I would guess that those not willing to shrink a LR tire simply do not know how or are too lazy to do it as it is usually much easier to stretch tires.
FWIW, shrinking a tire 1/4" is no big deal - shrinking it 1" can be a real chore!


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Carlson that is a good point having a consistent right side size. But I'm not sold that number has to be a "hard" 34". Ride height is going to vary with the weight of the setup i.e. 330 vs 425 and that 34" tire is not going to roll out to the same amount for both setups (unless we're taking the extra steps to measure roll out each time). I would like you said though pick and keep a consistent right side.
 
Now hold on . If your coming in at 425 and racing in a 330 class , Tire roll out is really not a concern .
I mean that argument againt keeping them 34 is invalid .
The difference would be miniscule . as far as how far your traveling per revolution .
If you have two sets of tires with differnt right side circumfrence , its not a big deal .
if you have 6 sets thats a little more concern .
every stagger change has a direct effect on your percentages which creates more effort to keep things consistent .
its not so much all tires have to be 34 vs 34.5 its the consistncy of the whole group of tires .
 
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Fwiw I'm running Burris 22 or 33 most of the time, I also have a set of Hoosier FK if/ when a Hoosier series race comes around. I mainly run in the FH 350 class, but I'm 40 plus pounds over. Front stagger usually 1.25", rear 1". Because of my weight difference I typically start with 5 lbs on left and 6 on right, sometimes more depending on the track. I'm not a front runner by any means but I've managed to get some top 3 and top 5 finishes. I appreciate everyone's input so far, and I had no idea that the chassis builders are going off a 34 inch right side. What about the LF, should it be the same size as the LR or does that not matter as much?
 
32.5 ---- 34
33-------34

That's the typical setup or baseline. Most end up with 32.5 or 32.75 LR and everything else is as close to baseline as you can keep it usually. Not too many times you'd need to vary off the baseline besides the LR. But, also most of the time keeping all the tires consistent isn't easy, so they'll all vary and 1/8th or more depending on how good you are at tire maintenance.
 
ENGRacing said:
Carlson that is a good point having a consistent right side size. But I'm not sold that number has to be a "hard" 34". Ride height is going to vary with the weight of the setup i.e. 330 vs 425 and that 34" tire is not going to roll out to the same amount for both setups (unless we're taking the extra steps to measure roll out each time). I would like you said though pick and keep a consistent right side.
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I'm not sure what you are trying to say here (highlighted above.)
A tire that rolls out 34" will be 34" no matter what weight the driver is.

Question: Do you run the same psi in both 330 & 425#?
 
When you call a tire 34", are you measuring the circumference of it on the stand or the distance traveled one revolution with the driver in the kart?
Both measurements won't be equal.

Flattop all how far you're traveling per revolution is is the circumference of the tire when under load which is proportional to the diameter of the tire. So again I'll agree with Carlson, consistency is important.

If you want ride height to be equal for any weight setup, you have to have equal rollout measurements to ensure the diameter of the tire is the same (by psi changes or grow/shrink).
 
The Circumference changes physically with weight on the tire ?
Please explain how you measure that difference .
It's 34 inches at 6 psi unloaded .
350# gives it 64# on the rr
425# is 78# on rr
whats the circumference change between the two?
If the circumference changes with weight wouldn't the tire pressure also change .
 
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ENGRacing said:
When you call a tire 34", are you measuring the circumference of it on the stand or the distance traveled one revolution with the driver in the kart?
Both measurements won't be equal.

Flattop all how far you're traveling per revolution is is the circumference of the tire when under load which is proportional to the diameter of the tire. So again I'll agree with Carlson, consistency is important.

If you want ride height to be equal for any weight setup, you have to have equal rollout measurements to ensure the diameter of the tire is the same (by psi changes or grow/shrink).
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I measure all my tires with a tape measure around the center of the tire while the tire is suspended in the air.
How do you measure it?
I don't see anyone marking the tire with chalk and then rolling the kart forward with the driver in the kart and measuring the distance between the two marks on the ground. I don't know of anyone who measures their tire size (karts or big cars) that way. I'll take the accuracy of my measurement every time over that!
Yes, the tire will conform (flat spot) to the ground from the weight of the car on it, but as soon as you roll the car forward, that flat spot moves ahead on the circumference of the tire (ie it is never measured.)
As far as the ride height changing due to different weight drivers...that can easily be accounted for with tire psi. You increase pressure for ride height and for controlling the amount of sidewall flex. I asked earlier, but I didn't catch your answer - Do you run the same psi in 330# & 425?"
 
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