Wheels?

Suspension, including wheel, tire and brake.
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mpdcop
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Wheels?

Post by mpdcop » 23 Aug 2010 01:13

I have the techno toy tuning front coilovers with 280zx struts and was wondering what size wheel would fit good under the fender without rubbing on the coilovers...my old wheels won't even fit, due to rubbing on the coilovers.. Thanks

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okayfine
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Re: Wheels?

Post by okayfine » 23 Aug 2010 07:27

You may have to adjust the height of your coilover perch, or go with a shorter spring. That said, 280ZX/T wheels should fit without issue, since you have ZX struts (which are quite likely the cause of your rubbing anyway, since the ZX strut hubs are narrower ~.75" per side and bring the wheels in).
Because when you spend a silly amount of money on a silly, trivial thing that will help you not one jot, you are demonstrating that you have a soul and a heart and that you are the sort of person who has no time for Which? magazine. – Jeremy Clarkson

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Dave Patten
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Re: Wheels?

Post by Dave Patten » 23 Aug 2010 08:13

Also, the center diameter on the 280ZX hub is larger than the 510, 70.3mm vs 66mm. Most aftermarket wheels are larger (73.1mm) so this won't be an issue, but it is something to check.

As okayfine suggested, you may need to use a shorter spring to raise the bottom spring seat to above the tire. This will allow use of a wheel with a higher backspacing or more positive offset. Generally a 4" backspace on a 15" rim will clear the 280ZX strut and the threaded sleeve, but not with a long spring where the spring/lower seat are beside the tire's sidewall.

I have a set of 15x6 wheels, +24 offset (4.44" backspacing) with 195/50-15 Dunlops. These are fine on a stock 510 strut, but they need a spacer to clear the coil over kit's threaded sleeve on a 280ZX strut. I will be using an 8mm spacer on my install. That works out to a 4.125" backspacing (+16 offset on a 6" wide wheel and +3 on a 7" wheel). These wheels (15x6 +24 /4.44" backspacing) with the 195/50-15 Dunlops appear to work fine on the rear.

My goal in using a 195/50-15 tire on a 15x6 wheel was to fit them under a stock, unmodified 510 fender.
Dave Patten
http://www.FutoFab.com
Dunbarton, NH

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banzai510(hainz)
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Re: Wheels?

Post by banzai510(hainz) » 29 Aug 2010 14:15

I have some Rota RB 15x7 +25mm with 195/45/15 Nexans

I just got the T3 coilover kit.
Order a 200pound spring in the 7 inch length size. Most sold are 8 in.

I will most likely mount the welded collar right on the old weld spot where the old Perch was. As this will be above the tire already
The alum threaded collar is 7 in long But Jeff Hino(icehouse) says you can mount it higher and just cut the rest off and true it up where the Gland nut is up on top.

Just by putting the T3 Camber plates youll lower the car another 1/2 to 3/4 of a inch as the stock ones are thick.

Im just hoping its not too low with the 7in spring. I might have to get 8in later. But Im really doin this to get rid of the positive camber in front since my car crash and get the tires to run even, Otherwise I was fine with my Susp Teq springs I had with koni D shocks

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Dave Patten
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Re: Wheels?

Post by Dave Patten » 02 Sep 2010 09:26

Tires and wheel selection has a lot to do with ride height and spring selection. Spring selection is sometimes a compromise. Longer springs give you more (and sometimes needed) suspension travel to prevent coil bind, but they also move the bottom spring seat lower where tire interference can be a problem requiring a higher ride height.

Let me share some information and where I am at with my particular front suspension install.

Here are the parts I am using:

Struts/Brakes - 280ZX
T3 Camber Plates
Ground Control coilovers and upper seats (w/bearings)
FutoFab LCA & TC Rods (currently set at stock lengths)
VTO 15x6 +24 offset (4.44” backspace)
195/50-15 Dunlop tires (22.7” dia)
Ride height, approximately 6.5" at the rocker (not weld flange bottom.)

Last night I did a quick bolt-up to see how much I needed to cut the strut tube to install my Koni inserts. I have a set of very short Koni Race inserts P/N 8610-1436, 11.42” body with a 5.62” stroke. Using the stock 280ZX strut (without springs or seats) I bolted the assembly together. The wheel/tire clears the strut tube by 1/8” at best; this is without the adjuster sleeve in place. With the threaded sleeve in place I planned to use an 8mm spacer, I may be able to drop the spacer thickness to as small as 4mm but final assembly will determine what that thickness will need to be.

With all the parts bolted in place I jacked the wheel/tire up until it contacted the inner fender well. To my surprise I found I still had strut travel left (now this is with no bump stop or upper spring seat in place). If the upper seat were in place I’d estimate the remaining travel distance at about 1”. So with a typical bump stop it will compress about 50% before the tire rubs the inner fender well using a stock 280ZX strut length.

All of this got me to thinking, why would I want to shorten the strut length if I am not in danger of bottoming the strut? I would need to be using a much shorter tire (well less than 22.7” dia) or modifying the inner fender to allow the tire to rise higher into the fender well to use the shortened strut’s travel. Neither of these things are planned.

Now if I use the Koni insert, it will need a spacer about 3 ½” long to make up the difference in strut to insert length (11.42” vs. 15.0” for a stock 280ZX insert). Using the Koni insert will also limit travel (5.6” vs. 6.75” for the 280ZX insert).

So I’ve decided to use the 280ZX strut at stock length, keep the inner fender stock and use an aftermarket strut insert like a Tokico sized for the 280ZX strut to keep the additional travel.

Then I started looking at spring length to keep the lower seat above the tire. Setting ride height at 3” from the tire rubbing allows for a 7” loaded spring height. Most folks use 8” springs. For sake of discussion let’s say the strut has to support 600# of car/passenger weight. A 200#-8” spring will compress 3” under that weight. This puts the actual loaded spring height at 5” in this discussion (or 2” shorter than is possible).

Another part of the equation is amount of spring movement. A 200#-8” Eibach spring has 5.3” of travel and 5.85” until it “blocks” which effectively means all the coils are touching and the spring becomes a solid stack of steel. If the spring compresses 3” from car weight and another 3” in bump travel (6”total), it effectively bottoms the chassis on the spring (steel on steel) not the bump stop, a very bad situation.

In this situation above, you have a 200# spring that compresses 3” under car weight. You have 7” of length that the spring under weight can occupy without the lower seat interfering with the tire so, a 10”-200# spring will install at a 7” loaded height (10”-3”) and work. If you use a higher spring rate the loaded height of the spring is more; ex. 250# spring @ 600# weight is 600/250 = 2.4” compression giving a 10” spring a loaded height of 7.6” which is too long for the 7” max height. The only way to fit a 250#-10” spring would be to raise the ride height .6”.

Recap of what I plan to use (remember, there are many variables in each application so examine all your particular details):
  • 280ZX struts at stock length because the tire hits the body before the strut will bottom.
  • 200#-10” springs, for the ride height I have chosen, the lower spring seats will still be above the tire and the spring will not coil bind before I bottom the suspension.
  • Spacer will be needed but the minimum thickness will need to be determined after the strut is completed.
  • Bump stop material and height may need to be varied to allow the most safe suspension travel.
Dave Patten
http://www.FutoFab.com
Dunbarton, NH

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