Backspacing Min and Max - 70 series

[TRAUTFEL]

I'm in the market for new wheels (steel) and have been trying to figure out what would be the ideal backspacing for 15x8 rims. I'm running 33x12.50 tires.

What is the recommended min and max backspace? I know 3.5 is stock. Would 2.5 backspace be too extreme? I'm trying to avoid spacers.

Thank you in advance for your comments. (I have a HZJ73 - with 2" Old Man Emu)

 

[yohavos]

I'm running 3.75" with 33x12.5's and they look good... I've got a set of 15x8 with 2.5" BS on order right now, I plan on running 33x10.5's on them though.

I had the 33x10.5's on the 3.75" wheels and the track width was too skinny with the OME springs on.

I'll post up when I get em on.

 

[TRAUTFEL]

Thank you Mike for your comment. I wonder how far out will the stick with that set of tires....under both tire size alternatives. I look forward to your picture.

I do want a wider stance but not necessarily an extreme skateboard look with half the tire sticking out or having too many issues with drivability. I know this set up will put some strain on the bearings but I see so many out there using a backspacing + spacers combo that nets a BS equivalent of between 2.5" and 3" that I wonder how many of them have actually experienced strain related problems.

Again I appreciate if anyone can post pictures of 2.5" backspacing or backspacing + spacers (netting 2.5) set up. Anyone running 33x12.5 on 15x8 wheels with 3.5 BS ?

Thank you again.

 

[prairiecruiser1]

I had 15x10 with 3.5 back spacing ang 33x12.5 MTR's looked good these were on my hjz77

 

[sadam_husain]

What is the recommended min and max backspace?

the more offset you've got the more stress you'll put on the wheel bearings but there strong enough to cope with the loading, I had a set of 8" rims we turned out and flipped the centres and I ended up with a backspace of about 30mm. I ran them for 3-4 years and now there on my mates daughters truck and havent had any bearing failures with them, I ended up with about 150mm wider track and was noticably more stable on and off road

 

[Malahki]

Ok I got three pics for you all with different rim/spacer/tire combinations.

1st pic: 16x8 rims w/ 2.75" backspacing 1" spacer and 33x10.5" Firestone? (winter)
2nd pic: 15x8 rims w/ 2.5" backspacing 1" spacer and 35x12.5" Mickey T's MTZ
3rd pic: 15x8 rims w/ 3.5" backspacing 1" spacer and 33x12.5" General Grabber

So the first two pics are of my daily driver BJ74 (OME 2.5" lift, extended shackles) with my summer and winter set ups. I've been running this way for a few years now (about 60,000km) and never had a problem yet.....and yes I do wheel it. I definitely like the added width on and off road and would like to go even wider but tha'ts going to take some work (widening axles and fender flares). The 3rd pic is of my BJ71 (stock leafs w/ extended shackles) that I sold

The only downsides to the width is obviously the tires are going to throw a lot more dirt and water onto the body and the tires are going to get into the sheet metal on your fenders on full flex instead of tucking inside. I've had the 35's at full flex rubbing too many times to count but its never been hard enough to do any damage. I now have a U-bolt flip kit installed up front and as a side effect its effectively increased the bump stop by 1" and stopped any rubbing.

 

[TRAUTFEL]

Thank your very much for posting those pictures! I actually thought that the 2.5 would stick out a lot more than that and you even have additional 1" spacers in there. 2.5s do not seem extreme at all..someone had told me tires would stick out over 4 inches.

Thanks again.

 

[yohavos]

The sun was actually too bright for me to get any good angles, but here's my 15x8, 3.75" BS with 33x12.5x15's on OME Dakar's.

New wheels (15x8, 2.5" BS) will be here Friday and I'll be going back to my 33x10.5x15's (as seen on spare):

 

[77cruiser77]

Question for BJ71 and yohavos:

What brand of rim are you using? I was talking to someone that even on a 2.5" backspaced rim that sometimes the backing plate can still rub the calliper so when I do upgrade my rims I want to make sure I do go with the right ones.

 

[Malahki]

Not following the question. Are you saying the mounting surface on the rim is going to rub the caliper? If you are, the mounting surface is flat and the distance to the caliper is not going change regardless of back spacing.

That said both sets of 15" chrome rims in the above pics were on the vehicles when they came from Japan so I don't know what they are. The black 16" rims with 2.75" B/S are ProComp Rock Crawlers

 

[77cruiser77]

Yes from my understanding that is what I was told from a Cruiser Vendor. It did not make sense to me but figured he must know more than me

I figured I'd just play it safe and find out what rims people are riding on instead of the backspacing specs

 

[yohavos]

Yes from my understanding that is what I was told from a Cruiser Vendor. It did not make sense to me but figured he must know more than me

I figured I'd just play it safe and find out what rims people are riding on instead of the backspacing specs

Just fitted the 15" Pro Comps I ordered and they did not clear my front calipers. After everything, I ended up going with spacers to make em work.

It widened my track width considerably, and I'm pretty happy with it. With that being said, if I was doing this all again I would take a good hard look at some 16" wheels.


Springs are OME 2.5" Dakars, wheels/tires are Pro Comp 15" Wheels, 2.5" BS, 1.5" Spacers, 33x10.5x15 BFG A/T's:

(forgive the street shots )

 

[yohavos]

I didn't think I would care for the black wheels, but the look is growing on me. I'm pleasantly surprised.

 

[TRAUTFEL]

Buyer beware...Hope this helps as a heads up for anyone buying pro comp rims.. ...I went to a local Pro comp distributor, I wanted to get a set of Rock Crawler rims ref# 98-5883R3.25 (3.25 backspacing) but they didnt have them in stock at the time and told me they could order them for me. I was concerned with the clearance of the front calipers and they told me to try for size one (same Rock Crawlers - 98 model) with 3.75 backspacing , I did ....and they cleared the calipers...then they told me a difference in backspacing with the same model would not change the clearance and diameter (mid and outer perimeter in the inside of the rim)...well based on this I decided to have them order them for me.

After more than 2 months ( im overseas) I finally got them and ..... they did rub the front calipers. When at the store, we compared the 3.75 rim that I had tried on fr size with the one with 3.25 bs. The rim has the same exact construction but the mounting plate is flipped around so that what normally is the outside face of the rim in the one with 3.75 bs (which has a narrower mid perimeter), in the 3.25 backspacing rim that face came in the inside.

I would had thought that the rim fr a technical reason is constructed in such a way that a change of backspacing would maintain the same overall structure (outside side and inside side and also where tire is fitted) when the rim model reference is the same...but instead it looks as if at procomp they had modified the rim by flipping the mounting plate around to get the required backspacing which I thinks is a pretty sloppy mod. for a reputable company such as Procomp. Ofcourse the structure of the rim where the tire is fitted is also flipped around when compared to the rim I tried at first. All this with two rims of the same model and brand just with different backspacing?!?!

They told me they will try to get procomp to accept this is a manufacturer construction error and replace the rims...we will see...

 

[nuakameba]

Pro Comp 52s

Another heads-up on wheels:

- in addition to worrying about clearing the calipers, you have to worry about clearance from the rear leaf springs. After installing a new set of Pro Comp 52 wheels (16x8 3.75in bs) on my 91 FJ-70, I was expecting to have to deal with the front calipers (a little grinding took care of it) but was not expecting to see that I had only 3cm of clearance between the new rear tires (185/75 R16) and the rear leaf spring. Had to buy spacers for the rear tires to get enough distance between them and the springs. I haven't seen this problem discussed much on the forum, but I would expect that it must happen often when moving up to wider tires and/or different rims.