legit 12.5 width tyres on 8s?

[Webbie]

Ive herd a few people saying that BFs , Procomps and MTRs are all leagally able to be run on 8s is this true (WRITTEN DOCS REQUIRED ) so i can decide with tyres i can run in this LITIGATION F@CKING WORLD we live in no jail wanted in the result of an accident as I would like my sphincta to remane its ORIGINAL size

[N*A*M]

for 12.5" tyres

bfgs and procomps have minimum 8" rim width recommendation from the manufacturer

gy mtr, coopers mt does not

there are others for each category too

still, you may be able to get a statement from the manufacturer (or the local distributor) to say they are okay for an 8" rim

[bogged]

for 12.5" tyres

bfgs and procomps have minimum 8" rim width

Last I heard BFG wasnt happy with 8in rims, thats wat was what Kev Williams was sprouting.. That was few mths ago though.

[hypo]

a 12.5" tyre is illegal but its metric evuqilant is

[mattc]

for 12.5" tyres

bfgs and procomps have minimum 8" rim width recommendation from the manufacturer

gy mtr, coopers mt does not

Are you sure? I thought the RTA's enforced what ever the tyre manufacturers specify in which case BFG and Goodyear specifiy 8.5" minimum rim width for their 12.5s whereas Cooper and Procomp specify 8"minimum. This is all according the spec sheets on the various manufacturers websites.

cheers
MattC

[Wendle]

your engineer just has to de-rate the load and speed rating accordingly.

[Shorty40]

What if your truck is too old to have a placard on it


BTW my engineers certificate says 35 BFGs on 15x8s is OK. So that is enough to get me out of the sh!t with Mr Plod

[Roktruk]

I think there's a disrcrepancy between what the manufacturer recommends, and what the Oz legalities say. I ran 33" BFGs on 15x8s and they were legal according to WA road rules, and I think with the National regs (can't remember what they're called now), but all the manufacturers seem to recommend 8.5" for 33's now. Gets back to wheel width and offset vs legal change in track of the vehicle.

[auto_eng]

The rules vary state to state on what you can run legally but they all require the rim and tyre to be an 'approved combination'.

The regulations covering tyre fittment allows you to use 'approved combinations' from sevral rim and tyre manuals. Australia, USA, Europe, England (and some more) have their own Tyre and Rim manuals. The most useful one in the "2003 Year Book - The Tire & Rim Association Inc" as it lists a lot more of the larger size tyres. This is the USA version.

For all different widths, profile and roll outs it list load ratings, inflation pressure and approved rim widths. If you take a 31, 33, 35 or 37 x 12.5 on a 15 inch rim (just for an example) the approved rim widths are

8 1/2" J
9" J
10" J
11" J

The 31 can also go on a 9 1/2" J

The 'J' refers to the profile of the rim. JJ rims cam be substituted for J rims with no probs.

As you can see 8" wide rims are not acceptable for a 12.5" wide tyre. The widest tyre I could see listed for a 8" wide rim is a 11.5" wide tyre.

Let me know if you want furter details/proof.

[auto_eng]

The rules vary state to state on what you can run legally but they all require the rim and tyre to be an 'approved combination'.

The regulations covering tyre fittment allows you to use 'approved combinations' from sevral rim and tyre manuals. Australia, USA, Europe, England (and some more) have their own Tyre and Rim manuals. The most useful one in the "2003 Year Book - The Tire & Rim Association Inc" as it lists a lot more of the larger size tyres. This is the USA version.

For all different widths, profile and roll outs it list load ratings, inflation pressure and approved rim widths. If you take a 31, 33, 35 or 37 x 12.5 on a 15 inch rim (just for an example) the approved rim widths are

8 1/2" J
9" J
10" J
11" J

The 31 can also go on a 9 1/2" J

The 'J' refers to the profile of the rim. JJ rims cam be substituted for J rims with no probs.

As you can see 8" wide rims are not acceptable for a 12.5" wide tyre. The widest tyre I could see listed for a 8" wide rim is a 11.5" wide tyre.

Let me know if you want furter details/proof.

[JK]

Now that's all fine and dandy... BUT where do you get 8.5 x 15 rims from?

What are the possible failure modes for a 33 12.5 running on an 8" rim?

BTW, thanks auto_eng for the clarrification.

[auto_eng]

I have seen 8.5 x 15" for sale. Have you had trouble finding some?

Modes of failure...rolling off the rim, separting from the bead maybe.

Just becaue the rim and tyre is not a listed combination is not a guarantee that the combination will fail but wouldn't like to try and explain my way out of it if they did fail.

[JK]

I phoned around when I was looking for rims recently but had no luck sourcing them. I was looking for a set of rims for my DD tyres which happen to be a second hand set of 33 12.5 R15s with about 10-15,000 ks of tread left on them. If I had found a set of 15 x 8.5 rims I would have jumped at them!!!

To ultimately get away from the 15x8 problem, I have chosen to purchase a set of 16x8 rims that I will ultimately run a set of 315 75 R16s on legally. I am currently running my 36" swampers on these rims until the 33s wear out and I can get the 315s.

Until then I have joined the ranks of the thousands of 4WDers in Oz running 12.5 tyres on 8" rims...

[MQ080]

8.5" rims can be bought, but too much bother

just get over it and run them on the 8

[bigsteve]

8.5" rims can be bought, but too much bother

just get over it and run them on the 8

Or buy the 8's and weld in a bead lock hoop = 8.5

[mattc]

Ahhh... but afaik 8.5" rims are illegal on most 4wds and can't be engineered according to the NSW RTA website.
http://rta.nsw.gov.au/registration/downloads/vsi09.pdf

Four wheel drive vehicles. For these vehicles, except where the original manufacturer provides to the contrary, the maximum wheel width is the lesser of the maximum for rear wheels on your vehicle or 204mm, the front and rear wheel wheel widths shall be the same.

204mm = 8" so unless the manufacturer spec'd wider than 8" from the factory....

We just had a big thread on AusJeep started by someone having to sell their 10" rims from their Wrangler after being warned by the local police to get rid of them

[MQ080]

That's interesting... cause in my RTA Vehicle Standards Information bulletin No9 Rev.2 Apr '98 it states: Vehicles built to comply with ADR24 (after1/1/1973) Tare weight of 1201 & over kg, allowable rim with increase above the widest optional wheel avaliable as original for the axle assembly used is 51mm or 2.0 inches, WITH certification of an engineers certificate...

[mattc]

MQ, the url I posted is the doc you mention and it does confirm what you said. However the way I read it, you must not only meet the vehicle age/weight restrictions but also the special conditions for FWD, RWD, 4WD, etc as appropriate. In which case greater than 204mm cannot be engineered unless factory fitted.

Just the way I read it - I'm no expert

cheers
MattC

[MQ080]

True it is vague... i think that's how the RTA guys like it The way I see it, there would be very few police that would defect for the 10". Coppers as a "general rule" (hear we go ) only are intrested in riceburners, whereas 4wders "usally" keep to themselves... But there is always a Highway boy who needs to fill his quota Therefore the only drama I see is insurance in an accident if the vehicle is towed.

In the mean time i have had a chat with 3 of the RTA inspectors at work and they said they would all pass it if it was cerified with a sig.

[robbie]

well I have spoken to a few cops (TMU's - the traffic ones) and asked them if they defect 4b's..

he goes "we generally dont go for fourbies unless they have those massive dirt bike looking tyres hanging out the guards"..

but yer, they dont normally target 4b drivers

[MQ080]

You would be hard pressed finding a General Duties cop that could write out a defect notice and the rest could not be all that bothered

[robbie]

haha I copped one years ago when I had my old celica from a 'generals duties cop'..

he couldn't find much, but he got me the bastard

[MQ080]

"Cops are Tops!"

[mattc]

You are probably right - anyway my 33's are only skinny 10.5s

I actually took my Jeep to the ACT RTA lunctime today to get the engineers certificate 'endorsed'. They told me I don't need the 'spray suppressors' the engineer spec'd since the gap between the tyre and the flare is not that big. Plus I don't need the cover I made for my roller fairleads either (engineer spec'd again) They said they are rounded enough and I should just hook the cable hook to the eylets under the bullbar rather than having it sitting snug against the fairlead.

Everything else a-ok

Chatting to the inspectors they said they really only bust 4wds with really big lifts and no mud flaps / not enough flares / rubbing / fouling etc - including vehicles that throw up too much spray in the wet....

However, they didn't accept my stat dec that I had changed my speedo drive gear and measured it against my GPS.... I have to go get a calibration certificate from a proper tester. Fortunately the mob that calibrate the taxi meters was not far and I am booked in for Friday. Once they have a copy of that I'm legal - woohoo.

cheers
MattC

[JK]

Chatting to the inspectors they said they really only bust 4wds with really big lifts and no mud flaps / not enough flares / rubbing / fouling etc - including vehicles that throw up too much spray in the wet....

Hmmm.... better get those rubber flaps on the 1/4 chop soonish

All you can see from behind is a FULL 33 / 36.

[Wendle]

They told me I don't need the 'spray suppressors' the engineer spec'd since the gap between the tyre and the flare is not that big.

your engineer, John Wilson I presume, only told you that because that was the last thing they tried to use an excuse to keep my car off the road a few months ago..

However, they didn't accept my stat dec that I had changed my speedo drive gear and measured it against my GPS.... I have to go get a calibration certificate from a proper tester.

They didn't understand the equation that I had written down to show that my non-standard ratios match my non-standard tyre size, so they couldn't argue that point with me..

[mattc]

Yep John Wilson, and yep he said someone had got knocked back so I assume he is just being conservative now.

[MQ080]

If bullbars arn't suposed to have anything sticking out from them i.e. fishing rod holders, how do we all get away with winches?

[mattc]

There is special mention of winches on the RTA guidelines for projections. The local RTA said 'cos the rollers are rounded it is ok (I don't need the protective cover I made). They don't accept forward facing driving light mounting tabs, fishing rod holders, fornt mounted towbars/drawbars etc - basically anything 'sharp'. The NSW RTA website has diagrams etc to explain.