Rear wheel width

[masracingtd1167]

I have been using a 12 inch rim with my 12 inch tires but I have a set of 10 inch rims that are super light . Just wondering if any one else has any experience with this ? The tires are the Goodyear 2585's Thanks Bill

[GlennLever]

Look the tire up on the manufacture web site and they should tell you what rim width you can use with the tire.

[dreracecar]

Go with the 10"  reason is that on the burn out the sidewalls will square up and the contact pattern on the surface will be even. Going with the 12" the tire will triangulate and concentrate harder in the center of the tire surface

[JrFuel Hayden]

Bill, for years we ran 12" tires on 10" rims, but as we started running below 7.20's I found we needed a 11" rim, mostly for the finals at Bakersfield when the sun went down and the track cooled off. Then as we made more power, we were using the 11"  D2585 combo more based on the tire speed I saw on the RacePak computer. So then I made-up a 12"/ D2585 combo for declining tracking conditions. The wider rims also were needed not only for the start-line, but also when the car would move around at half track. The wider rims kept our 60' times 1.01 - 1.04. The down side of wider rims is the tires will not grow as much, so the MPH is lower. As a matter-a-fact one of the Heritage J/F racers racing the lightest car [1355#] & running with the smallest motor [ 387ci ] doesn't like to run 12" rims because of the slower MPH, but then again he's running canard wings to try to get a hold of the track around the 1/8 running on his 11" rims. 
BTW we run 5 3/4 to 6 1/4 lbs of tire pressures, and launch at 6,000 to 6,400 rpm. I had Bogart widen our 10" rims to 12" because we don't use the 10" anymore, only the 11" or 12".
So, use your light 10" rims until you have traction issues, because racing a JrFuel type car, you need tire speed to keep the motor in the RPM it will work best. Case-in-point if your 60' are above 1.15, use the narrower rims and raise the launch rpm, and maybe lower your tire pressure to increase your tire speed. As you lower your tire pressure the tire will concave in the center and run more on the edges. To confirm that check your tire temps right after your run, going across the tire tread with your temp gun, you can see the temps are higher on the edges. I always check the tire temps when I pick-up the race car after a run. I also check engine temps just before final staging and after the run, so I get an idea what to change for the next run.
I can see Bruce has good results with his blown alky SBC on 10" rims using 33" tall tires [ I think] because he's making different power at different points in the track than our injected alky 400 ci SBC's.
Glenn's point about asking GoodYear what rim to use, is a good idea, but for the D2585's their chart says 12" rim, and they are conservative suggesting wider rims for more traction. GoodYear has told me "use rims only 1" on each side of the tire size", ie 12" tire use no less than 11", and no more than 13". Racers still have to decide what combos work best for them.
Feel free to call me with any questions, 805-444-4489
Good Luck racing,
Jon 

[Paul New]

Great information Jon!

[wideopen231]

Great info to have and some good tuning tips there Jon. Unlike jr fuel combos where quicker every past is important I am mainly concerned about every run being exactly the same.   The wider giving better 60' and being better for traction all around is what I can use.   My engine combo being  526 aluminum Hemi,glide w 6400 stall,3.90 to 4.10 gear. In 225" slipjoint chassis and hopefully stay around or below 1600 lbs ,can't afford a titanium show place but I do try to keep weight off anyway I can. 


   My plans are 15x14 wheels bead locks.Yea heavier but has to be worth the weight.Seems the lite weight preacher(Parks) has them and the canards.If Parks will run them with added weight I figure they have to out perform the weight cost. Plus I have a set of wheels that can be converted to them at half the cost of new bead locks,due to design of wheel 14 is as small as weld says they can cut them to.

 If that combo has something that is stupid about it let me know.New to FED and working towards getting setup dead on first time out,yea I know aren't we all.

[JrFuel Hayden]

I believe Parks runs bead-locks because their motor combo makes less torque than other J/F cars and in order to keep the tire speed up so it doesn't pull the motor down out of the RPM range it needs to be, they run as low as 4 1/2 lbs of tire pressure. So with that kind of low pressure you'd need bead-locks.
Now about your combo; what kind of HP are you making ?  With your 526 I assume you are using a 8" or 9" converter, I also assume your 526 makes more torque than our 400 ci SBC and early iron Hemi, [ I just picked-up our 354 block from the machine shop] , so that's why you plan on running a 14" tire. With your 3.90-4.10 gears what kind of RPM are you thinking of running thru the 1/4 ? I also assume your 6400 stall is close to the RPM the "cam" comes on. I've seen many a combo where the stall is too low and the motor struggles to go from stall to where the cam is designed to work.
We have also learned that stiffer chassis deliver better ET's unless you are running Big Show Top Fuel. You might want to call Parks about chassis combo's and they have someone that can covert you wheels to bead-locks, maybe for less $.

Jon Hansen, 805-444-4489

[rooman]

On the subject of converting wheels to bead locks I can get them done here in Indy for $950 a pair, double bead lock with black 12 point bolts. Stainless bolts run another $80.  (and they don't cut the original rim up with a cut off wheel like the guys at the NMCA etc events ). My guy says that he can do most Welds to about any width.

Roo

[masracingtd1167]

Jon Great information ! One of my biggest problems has been not getting enough wheel speed with my car . Another issue is my motor placement . When Frank built my car in 2003 we decided to put the motor out 36 inches . I think most every car now is about 50 inches . My car is also a little heavier than most JR fuel cars . When I was spraying it with nitrous to run Top Dragster it weighed 1585 with me in it . I have started to take weight out of the car so far I am up to 133lbs and about 25 lbs of it is rotating weight! I think I am going to give the 10 inch rims a try . Thank's guy's for all the info! 

[wideopen231]

Hp should be  little over 1000 hp might edge upto 1100 according to few programs I have run combo thru,no real world dyno yet.Programs call for mid 1100 range but I figure little less is more realistic.Power starts to come on around 6000 up to about 8500.Shifting around 7500 to get it to fall back just above converter and near max torque numbers.278/285@.050 and 820 lift.Mildly reworked BAE heads,CMC injection(Chris McBride Custom) All of this is calculated not actual dyno numbers,got to start somewhere.Not beiggest believer in computer numbers but these programs do get dang close to real dyno number if you give them proper info.I hope torque is more than sbc. I know the Jr. Fuel sbc stuff is high dollar and big power ,but 4.5" of crank had better make some torque or the engine builder will catch crap(yea thats me).Also have nitrous system thats good for 400 to 500 hp,not full time use on it .

 As for chassis I can stiffen this one with few bolts being tightened up. Slip is in uprights and one top rail in front.I have jacked it up 6 inches with no bolts and frontend still on  ground,extreme yes. Tighened it all up and front came up with very little arc in chassis. Plans are to start with stiff and get ironed out then play with slip some.

[wideopen231]

When get ready to convert wheels I will check with Parks and get number from Rooman.Like getting info ahead of time but not bothering someone till money is here for the work to be done.