D2554 Circumference consistancy

Technical and Repair Discussions
User avatar
Forum Hermit
Forum Hermit
Posts: 128
Joined: Thu Dec 01, 2011 8:35 pm
Location: Hebron, CT
Chassis:
008
Facebook Page:
https://www.facebook.com/profile.php?id=1032406508
PostPosted: Sat Jun 27, 2015 6:33 pm
I ran my first set of D2554 tires a couple of weeks ago at LRP. I corner weighed the car prior to the race and had to make, what I thought, were significant adjustments. That surprised me since I had not changed anything since May @ NHMS. My RF ran out of camber adjustment which has never happened before. (could not get below -2.5)
Through the weekend at LRP the LR tire was just not coming up to pressure as I expected (that's the one working hard at LRP).
Today I measured circumferences. I have three tires at 71 5/8 and one which is 71 1/8 (checked three times) all measured at 29 psi. The small tire is one of the rears. Unfortunately I forgot to mark the corner on the tires, D'oh!
Is anyone else noticing differences in tire diameters? Bob Breton alluded to it in one posting.
Thanks,
Last edited by xvracer on Sun Jun 28, 2015 7:30 am, edited 1 time in total.
Les Kurz
NER SRF #31
Chassis #008 (GEN2)

Needs a Life!!!
Needs a Life!!!
Posts: 260
Joined: Wed Feb 08, 2012 8:45 pm
Location: Daytona Beach, FL
PostPosted: Sat Jun 27, 2015 8:07 pm
Yes I have seen the 2525 and the 2554 tires like this. I have tried to do as I did when I short track raced and we could pick 4 tires off rim at a size and when mounted they would be right where we knew they would be. We ran stagger in circle track. Not so much here. I would find sometimes 1 in 4 being as much as 1/2 inch diff. When I tried to find 4 the same size in Goodyear trailer and had them mounted at the same PSI I would find them to be off. So it can be a crap shoot. You can check them before running them and then ask Goodyear to try a different tire. They never look like they like this but we have new tire people now. A tire being 1/2 inch diff. in size will change corner weights and also the way the car handles.
User avatar
Needs a Life!!!
Needs a Life!!!
Posts: 766
Joined: Wed Nov 30, 2011 1:03 am

Chassis:
098
Facebook Page:
http://www.facebook.com/#!/denny.stripling
PostPosted: Sat Jun 27, 2015 9:49 pm
I've had larger than 1/2" variance (I saw ~1" one time) on multiple occasions.
____________
Bay 12, please.

Needs a Life!!!
Needs a Life!!!
Posts: 211
Joined: Tue Nov 29, 2011 11:32 pm
PostPosted: Sat Jun 27, 2015 10:19 pm
Other than searching through a pile of tires for 4 that may match up is there any other way of compensating for this difference?

Ready to Write a Book
Ready to Write a Book
Posts: 66
Joined: Wed Feb 01, 2012 3:48 pm
PostPosted: Sun Jun 28, 2015 12:41 pm
When I raced FV the tires were marked pre mounting for their circumferance. I am not sure if that was done by Hoosier or the tire supplier. Getting a close match between the tire sets made a difference. I haven't seen that done on any set of SRF tires as yet. Perhaps it should be as either a courtesy or standard practice given the amount of tires we as a class tend to buy.
User avatar
Needs a Life!!!
Needs a Life!!!
Posts: 767
Joined: Wed Nov 30, 2011 12:21 am

Chassis:
595
PostPosted: Sun Jun 28, 2015 4:32 pm
If you have time consider over inflating the smaller tire overnight to stretch the tire a bit. Otherwise, adjust corner weight as needed. Not sure why you would be making a camber adjustment to adjust corner weight; I would expect 1-2 turns up on the corner with the smaller circumference would be sufficient since you're only talking about 1/12" in radius change for 1/2" in circumference.
Bob Breton - SRF 51 - San Francisco Region
User avatar
Forum Hermit
Forum Hermit
Posts: 128
Joined: Thu Dec 01, 2011 8:35 pm
Location: Hebron, CT
Chassis:
008
Facebook Page:
https://www.facebook.com/profile.php?id=1032406508
PostPosted: Sun Jun 28, 2015 8:47 pm
The camber adjustment was because it was reading high (-2.4) not strictly to adjust corner weight. I put it up on the scale pads today, RF ride height is 1/2" out from the rest. The "small" tire is on the LR. Guess I'll start from scratch with the Mumm Bros. procedure again.
Les Kurz
NER SRF #31
Chassis #008 (GEN2)

Forum Hermit
Forum Hermit
Posts: 161
Joined: Sat Dec 03, 2011 1:03 pm
PostPosted: Mon Jun 29, 2015 8:29 pm
one tire was over 3/4 inch larger at the sprints

I returned it- they will take it and exchange if more than 1/2 difference- less than that you pay a fee

FYI

Former Specracer National Champion
Former Specracer National Champion
Posts: 204
Joined: Tue Jan 24, 2012 7:23 pm

Chassis:
541
Facebook Page:
www.facebook.com/mbiracing
PostPosted: Tue Jun 30, 2015 2:35 pm
Corner weight changes and differences in camber readings can easily be effected by the smallest of curb "kissing" or even a dropped wheel. A bent upper ball joint bracket I think is the most common culprit. I would look at your rocker arms too, that could change a ride height reading. You don't have to make contact with anyone to "adjust" these items. I would look into suspension components way before I would measure tires. Also check your wheels when measuring camber, especially Welds. A slight bend in the wheel can give you up to a 1 degree swing in camber.

Also for the corners on the tires...look at barcode. If the barcode is on the outside, it is the RR, if it is on the inside, its the LR. This is the normal GY mounting procedure. I wouldn't worry too much about this either though. I put the left on the right and the right on the left and run it all the time.

I used to measure my tires, but then if they were off I would always "think" too much about it.

Return to Technical and Repair Discussions

Who is online

Users browsing this forum: No registered users and 12 guests