Ultralite 15 x 10 wheel backspacing for slicks?

[MudHut]

I've been searching for a while to try and find an Ultralite owner that has mounted 15 x 10 inch wheels on their Ultralite all the way around for mounting slicks for autocross. I've seen pictures! Has anyone definitively identified a proper backspace on these cars? I have a sneaking suspicion that the backspace is very car specific.

Mounted on the front now is a 17X8 et48 +5mm spacer (225/45) that is equaling out to be about a 53mm total offset. About 6.6" of backspace. The fender bracket mirrors the tire sidewall well and is within mm's of touching the combo mounted now. The rear is no problem.

Thinking with the drop in OD to 23" with the slick from a 25" currently mounted, I'm going to be lower on the fender bracket, control arms are not an issue, nor is balljoint, I'm thinking 15 x 10 with a 5" backspace. Slick is a Hoosier 23 x 9.5 x 15.

Hmm. The overall width of the track will gain inches, that's a good thing. Will it fit through the door of my small enclosed trailer with these mounted? Decisions, decisions. Thanks for listening to me hash this out.

 

Jay

[xcarguy]

Jay, check with Roman (RGTorque). Pretty sure he can give feedback.

[MichaelD]

place a straight edge on the outside surface of your brake rotor. measure from the straight edge to the nearest contact point inside. That is your back space.

 

Don't forget to add a little more allow for squat of your tire sidewalls as they get wider as you power through turns.

[US Texas 7]

My S2K has original 17 x 8 wheels but original owner (Chuck Spera) I believe raced with 15 x 10. Mine has been changed to 10 inch brake front and inboard rear. I don't think 15 inch wheels will clear the standard 12 inch brakes/calipers. Fender bracket clearance may not be the only problem. I recommend checking with someone that has run 15 x 10 wheels on a Ultralite.

 

Robert F.

[MudHut]

I cannot find the ID of the 15" wheels I am looking at, so I cannot just measurement is out. I identified the brake package on the front of the car currently. The rears are smaller, so fit front, fit rear. The Wilwood package consists of the Forged Dynolite caliper with a 12.19" rotor. I stumbled around on the website until I found a 'kit' with those specs, 15" wheels are listed as do-able. Backspace for the smaller dia. wheel/tire combo puts it at a conservative 5" backspace, so I don't have to remove the front fenders. I have a 12x7 enclosed trailer that I used with a previous car, The Ultralite fits in with minimal room now, the kicker is it's not going to just easily roll into the enclosed trailer. Adding 10" wheels with 5" backspace makes the car wider overall and it misses getting through the door by about 2" on the rear axle. I could order the rears with more backspace but it would inhibit easy rotation. I'm ordering on Monday, so I'll have one more opportunity to get specs from the wheel manufacturer to double check the 15" will fit. Thanks for the suggestions.

 

Jay

 

 

BTW, Hoosier just dropped a bunch of slicks to the discontinued list, prices fall by 2/3, shipping is 15.00.

[MudHut]

Follow up:

 

The Bassett 15"x 10" wheels with a 5" backspace work well on the car, do not make contact or rub and are square and can be swapped front to back.

 

http://i356.photobucket.com/albums/oo1/JHogan/Super%20Seven/IMG_3837_zpsoff5bf2v.jpg

 

Jay Hogan

[xcarguy]

Jay,

 

Nice color combo all around. The new wheels go well with the red, black and silver theme. :cheers:

[RGTorque]

Follow up:

 

The Bassett 15"x 10" wheels with a 5" backspace work well on the car, do not make contact or rub and are square and can be swapped front to back.

 

http://i356.photobucket.com/albums/oo1/JHogan/Super%20Seven/IMG_3837_zpsoff5bf2v.jpg

 

Jay Hogan

 

wow, fancy lookin car right there. any more info?

[MudHut]

http://www.usa7s.net/vb/showthread.php?10617-WCM-Ultralite-S2k

 

Had my first autocross outing. Superfun.

[yellowss7]

Well, How did you do? Any Video? Tom

[MudHut]

Very first autocross in this car. Helpful comments are welcome.

 

My competition in this region is a fully tricked out Honda CRX on very wide slicks. Missed beating him in this maiden, choppy, bad placement, can't decide a gear, not looking ahead run by .3 sec.

 

A driving comparison from the FF Dulon from last year. Same lot.

 

Jay

[Kitcat]

Lose the passenger:)? Wow, big and bumpy course. Auto-x time is the sum of 100's of tiny decisions, nothing seems obviously bad, you will get smoother w/ more seat time.

[loudes13]

I'm the old owner and new owner of this car (long story)...

Anyway, I'm tempted to try 15" wheels for the street too. The 225/40/17 & 255/40/17's are pretty tall and shorter 23.5" tires would reduce the gearing nicely.

I just need to figure out the right wheels. A 15x8 and 15x9 or 10 combo with some trackday type DOT's would be great. Since I don't drive it in the rain the Maxxis DOT semi slick 225/45/15 & 245/45/15 would be perfect for street and the rare autox or trackday. I have a roadrace miata, so I don't need/want another racecar.

I see Jay ran 5" backspace, but I do want to keep the tires just under the fender to reduce rock/sand spray. I might just buy the tires and mount a couple on the current 15x10's just to measure. Unless someone here has already done some research.

Any suggestions?

http://www.usa7s.net/vb/attachment.php?attachmentid=12788&stc=1