'95 Sierra: setting up suspension to clear 31's

[davidsuzuki]

Sorry, when I'm tired I often get confused. I should have said increased turning circle from the adjusted.steering stops. But as you've said it won't be noticable so I'll continue planning for 31x10.5 and it sounds like a 15x7 rim with 0 offset will be the best size. I was suprised to see though when i put the tyre size figures through the calculator that going from a 205x70x15 to a 265x75x15 is only a 16.5 % increase. So if I want my speedo to read correctly, 4.9gears will be the go right?

[gwagensteve]

Speedo will still read 16.5% out. The speedo drive is after the reduction in the transfer case so even though the gearing is corrected, the speedo only reads the combination of tyre size and axle ratio.

Steve.

[davidsuzuki]

Hrmm.. just found some nice 15x7"s that are 5x139.7 BP but the offset is -9mm and the backspace is 3.625". From what lbzook is saying 31x10.5s are going to stick out beyond the flares by 9mm each side is that correct??

[lbzook]

Ok, I've pulled a wheel off this morning and measured my offset a bit more accurately and I'm actually on +7 rims.

My stock flares are long gone, but my tyres need about 4" to completely cover the tread.
So based on that, -9 rims would put each tyre out another 16mm, effectively increasing your track 32mm. Which would need around 116mm to cover. I would check how much cover the stock flares give off the guard and go from there.

Also in regards to my earlier comment on BS, I was a bit off, apparently 4" bs on 7" rim is equal to 0 offset, just for a reference.


Leigh

[jono165]

My 31's are on 15x7 -13 rims. The side wall lugs only just clip the springs on full lock. The tyres stuck out about 40mm past the edge of the factory widetrack flares.

[davidsuzuki]

Just occured to me if I go for a 245x75x16 tyre on a 16x7" rim I'll get a much wider choice of compatible rims and I'll keep the same tyre diameter of aprox 30.5" but shave an inch off the width 10.5" down to 9.6". With the right offset should clear the springs and keep within the flares I reckon. Any reasons not to move up to a 16x7 rim on a Sierra??

[gwagensteve]

A)Cost. Rims and tyres are both dearer
B) off road performance. Most 245/75's have a very high load rating as they are a common size on US domestic pickups. This makes they tyre less flexible on a light car, and you'll have 0.5" less sidewall to deform. This is good for road handling but will hurt offroad. Both tyre and wheel are also likely to be heavier.
C) there's fewer tyres in 245/75 than 31x10.5.
D) I reckon you'll struggle to get the right offset in 16x7. Most 16" rims have lots of backspacing.

If you really want a 16" rim I'd recommend a 16x6 or 6.5 and a 235 85 16. These are near 32", but look small because they are narrow and are correspondingly easy to fit. Rims could be superseded Grand Vitara take offs.


Steve.

[davidsuzuki]

Hrmm.. I've been looking a running a 30x9.5x15 to get around the width problem. Will I be able to air down sufficiently if I run that tyre on a 15x7 rim?

[davidsuzuki]

Hey Guys,

I'm picking up my OME lift kit from ARB on Monday and then I've got 8 days off work to get it installed. How long do you guys reckon it will take to install the kit. I've got nowhere to work on the car at my house so I have arranged access to a friends hoist in their car workshop. They're asking me how long I need it for and I'm not too sure. How long should the job take??

[gwagensteve]

I assume if you have a hoist, you also have access to a compressor/rattle gun?

If so, I'd be very surprised if you couldn't do it in about 2 hours. Especially as your car is clean (as in you don't have any existing off road damage or modifications)

I think we installed a complete suspension kit in Jonfromhamiltons car, without a hoist, after a trip (i.e we were tired and the car was muddy) in about an hour.

16X Ubolt nuts, 8X shackle/spring bolts, 8X Shock nuts - it's no big deal.

Steve.