33" tyres on 7" rims

Post by **curzzadude** » Fri May 14, 2010 11:37 pm

do 33x12.5x15 all treain tyres fit on 15x7 sunrasier rims for a 60 series or do i have to step up to an 8" wide rim???

Post by **Warnie** » Sat May 15, 2010 9:09 am

They will fit on it phisically, but the bead might pop off if any real force is put on the tyre. also it is illegal. A 12.5 inch wide tyre must be fitted on at least an 8 inch rim.

Post by **Gwagensteve** » Sat May 15, 2010 9:13 am

I think you'll also find that technically an 8" rim is illegal for a 12.5" tyre too. from memory the minimum legal size was something funny like 8.5 or 8.75, even thought the tyres are happy on 8's and everyone does it.

I agree though that 7's are way too narrow.

Post by **mavzilla** » Mon May 17, 2010 1:58 pm

yes they fit and they work fine,

Post by **Gwagensteve** » Mon May 17, 2010 4:26 pm

mavzilla, I'm sure that a 12.5 fits on a 4" rim too, but that doesn't make it right.

7" is far too narrow for a 12.5" tyre. The bead seat angle is all wrong making it easier to loose a bead and the pinching effect makes the angle between sidewall and tread excessive leading to reduced lateral stability and excessive bead bulge (which will be a problem with a 60 series as the tyres will rub on the inner guards at the rear - common with 12.5's even on 8" rims)

It's not recommended for a reason - and we're not talking about "nearly" the right size - a 7" rim is 1.5" too narrow.

Remember, even an 8" rim is technically too narrow for an 12.5" tyre.

How do I know this stuff? I have 12.5's on 7.5" rims (beadlocked 7's) and the inside bead isn't happy at all. Likewise, I've seen the inside bead go on other 12.5's on beadlocked 7"rims because of excessive sidewall bulge.

Steve.

Post by **Matt_85Lux** » Mon May 17, 2010 7:41 pm

Gwagensteve wrote:mavzilla, I'm sure that a 12.5 fits on a 4" rim too, but that doesn't make it right.

7" is far too narrow for a 12.5" tyre. The bead seat angle is all wrong making it easier to loose a bead and the pinching effect makes the angle between sidewall and tread excessive leading to reduced lateral stability and excessive bead bulge (which will be a problem with a 60 series as the tyres will rub on the inner guards at the rear - common with 12.5's even on 8" rims)

It's not recommended for a reason - and we're not talking about "nearly" the right size - a 7" rim is 1.5" too narrow.

Remember, even an 8" rim is technically too narrow for an 12.5" tyre.

How do I know this stuff? I have 12.5's on 7.5" rims (beadlocked 7's) and the inside bead isn't happy at all. Likewise, I've seen the inside bead go on other 12.5's on beadlocked 7"rims because of excessive sidewall bulge.

Steve.

Not only that but they will also wear on the edges due to the bulging. Put them on 8s

Post by **mavzilla** » Fri May 21, 2010 8:27 am

didnt say it was right ,but they have worked fine for years for me and have seen others with the same and no trouble.

Post by **mavzilla** » Fri May 21, 2010 8:29 am

8 inches would be better of coarse

Post by **SIM79** » Fri May 21, 2010 10:33 am

mavzilla wrote:yes they fit and they work fine,

When I bought my car it came with 15x7s fitted with 33x12.5 and it didn't handle well onroad, when I reaslised the rims were incorrect I fitted some 15x8s handling improved.

Post by **351ciofgrunt** » Fri May 21, 2010 11:28 am

SIM79 wrote:
mavzilla wrote:yes they fit and they work fine,
When I bought my car it came with 15x7s fitted with 33x12.5 and it didn't handle well onroad, when I reaslised the rims were incorrect I fitted some 15x8s handling improved.

Yeah I can imagine there would be alot of tyre roll around corners when running 12.5's on 7 inch rims

Post by **arnijr** » Sat May 22, 2010 9:09 am

My 33x12.50R15 BFGs are fine, on 10 inch rims.

Post by **GQ WAGHOON** » Sun May 23, 2010 10:53 am

Have to agree with mavzilla. 8" rims would be better, but I also have run 7" rims for years now with 33x12.5's and have found that they are OK. Been like that for the last 50,000 k's and never had any problems, with even wear and good handling. A cousin of mine has the same rig (LWB GQ) with the same tyres but on 8" rims. Handling is the same, but he has popped the bead quite a few times, and we both run the same tyre pressures to see if there is any differences between the two. Go figure.

Post by **-Scott-** » Sun May 23, 2010 11:36 am

Interesting.

Inside bead or outside? Front or rear?

I would guess outside front is most likely to go?

Are the rims the same brand? Are they both JJ? Do you both drive identically?

Post by **GQ WAGHOON** » Sun May 23, 2010 5:28 pm

A combination of all of the above. His brand of rims are Kings, mine are factory (stock) Nissan 15x7's. Our driving styles are similar, but I might give it a little more stick on occasions.

Post by **grazza** » Tue May 25, 2010 12:40 pm

I have 33x10.5x15 in 7" rims. BFG MT's - BFG are the only ones who make this size (I have been told)

Post by **Ruffy** » Tue May 25, 2010 12:46 pm

Check here: http://www.carbibles.com/tyre_bible_pg4.html

It will give you the rcommended rim size for tyres.

Post by **RO8M** » Tue May 25, 2010 1:04 pm

-Scott- wrote:Interesting.

Inside bead or outside? Front or rear?

I would guess outside front is most likely to go?

Are the rims the same brand? Are they both JJ? Do you both drive identically?

What's the JJ mean, Scott? is that the Bead seat type?
-Break, go google, find this:
http://www.rx7club.com/showthread.php?t=273857

jimlab on that rx7 site wrote:"JJ" refers to the shape of the wheel's flange (lip which holds the bead of the tire).

JJ = 18.0mm high x 13.0mm wide, with a 13.0mm radius
J = 17.5mm high x 13.0mm wide, with a 9.0mm radius

Plus these this funky pic, totally off topic...

Post by **-Scott-** » Tue May 25, 2010 8:26 pm

RO8M wrote:
jimlab on that rx7 site wrote:"JJ" refers to the shape of the wheel's flange (lip which holds the bead of the tire).

JJ = 18.0mm high x 13.0mm wide, with a 13.0mm radius
J = 17.5mm high x 13.0mm wide, with a 9.0mm radius
Plus these this funky pic, totally off topic...

OK - that's different to my understanding of it.

I thought

the "J" and "JJ" refer to "safety beads" - which apparently have a different shape to a "normal" bead, and are supposed to retain the tyre better.
A "J" rim has a "saftey bead" on one side only.
A "JJ" rim has a "safety bead" on both sides.
Offroad recreational vehicles are supposed to be fitted with "JJ" rims.

But I sometimes lack understanding, so I'm probably wrong.

Post by **danssurf82** » Thu May 27, 2010 9:29 am

i have 31x10.5x15 on 15x5.5 rims:) no problems in 3 years, can let then down to 6psi without breaking a bead... had a set of 31x10.5 on 15x7 and at 8 psi would break the bead.

Post by **bazzle** » Fri May 28, 2010 8:16 am

If its height your after(3") have a look at 255/85/16

http://www.miata.net/garage/tirecalc.html

Bazzle

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33" tyres on 7" rims

33" tyres on 7" rims

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