The wheels & tyres on my 900T are long past redemption and I need to move up from 12" rims to allow for the disc brake upgrade.

Current set up is 4"x12" shod with 155/80SR12
PCD 4x98 - pretty standard for Fiat
Centre bore 58.1mm

I've been using the following websites in order to work out the size increase in order to keep the speedo accurate:

http://www.carbibles.com/tyre_bible_pg4.html
http://www.brick-yard.co.uk/forum/tyre-size-for-rim-width_topic60146.html

I'm down to two choices as follows:

5.5"x14" with 165/60R14
or
5.5"X13 with 165/70R13

Both options offer loads more tyre choices and often cheaper than having to get 12" tyres in.

Note: 5" wide wheels don't appear to be very popular, or only come in 13" rims.

All good so far but the final piece of the puzzle is finding out the offset for the 12" wheels. I've search through all the manuals I have, on the wheels and searched the web but the best I can come up with is a range between 30 to 40mm.

Does anyone out there know what the offset is for the 12" wheels?
Or has anyone swapped up to a 13" or 14" wheel and would be happy to share their choice of wheel & tyres?

Incidentally, I'm hoping to fit something like a late 1970's Wolfrace type wheel or similar unfussy style.

my 84 pandora came with bbs alleycat style wheels which the vendor told me were fiat x19 wheels? in a weird twist of fate, some time later i was able to buy the set of steel wheels and tyres off the original owner of my van which he says were the wheels originally off my van!! not sure of sizes ( i believe later vans were 13 inch?) but i will check for you.

As far as I'm aware the 900E vans had disc brakes and needed 13" rims.
I've got hold of a set of 850 Spider front disc assemblies which appear to be a swap out for the front drums on the 900T. I've offered them up to the 12" wheels and there isn't enough clearance. I can probably get away with 13" rims but thought I may as well go to 14" as I have to replace the wheels & tyres in any case - and having a bit of extra space around the discs and callipers won't be a bad thing.
Once I can get hold of the offset (ET) value on either the 12" or 13" wheels I can work out what offset is needed on the new wheels to make sure that they don't foul anything.
The ET value is supposed to be stamped on the wheels but I'm guessing that the 900T wheels are so old they didn't have to do this at the time.

I'll check what mime have stamped on them tomorrow. I have original 13" ers over discs. I'm sure I read somewhere that they are the same or similar to Panda Mk 1s...spare discs and pads are certainly cheap.

I can't find anything stamped on the wheels despite later stripping the paint in the centre of the one photographed. For the record they are listed as
4&1/2Jx13.
By offset I presume that means the measurement from the outside of the inner rim to the back face of the wheel centre. I
make that 115mm. Hope that helps.

Hi Peter
Thanks for the information - to state the obvious - I didn't even think to get the tape measure out Doh!

If I understand the Car Bibles website correctly (link earlier) the offset is the distance the back face of the wheel set is away from dead centre.

As you have 4.5" width wheels - 114mm. A zero offset would mean that the distance in from each side would be 57mm. The width appears to be measured from where the tyre sits.

However, logic suggests that as long as the measuring points on both side of the wheel are the same in theory you should be able to simply subtract the smaller figure from the larger one and the difference will be the offset.

I'll get my tape measure out at the weekend and post my results in due course.

Cheers

Re: Wheels & tyres

My mind is boggling..My maths not as good as my welding!

Re: Wheels & tyres

Just found this on YouTube:

Makes it simples... not sure why they didn't use a tape measure with mm on

Re: Wheels & tyres

Using the method in the video I get an offset of 41mm.
Based on the information I found online earlier, the range for Fiat wheels was 30 to 40mm so I'm going with the 40mm top end.
I'll post details of my final wheel choice once I've decided.

I hope the information helps others.

Hi Gary

Same 900t again

we last summer fitted 131 miriafiori 13 inch steel wheels(silver and black) and 165/70/13 tyres and it works perfectly according to our sat nav speedo.

If you measure the with of the wheel inside where the tyre fits, 4.0 inches in your case or 102mm. take half of it at 51mm.

then measure from the bolt face on the back of the wheel to this centre point measured first.

to be fair most Fiat wheels at 13 inch will be slightly offset outwards.

i would definitely say you will feel the difference when you go for lower profile tyres

right, off the the braking post next

hope this helps

Tim

Hi Tim

Thanks for this and your other posts.

Out of interest, a chap call Tim helped me out around 10/12 years ago but that was through the Classic Camper Club. You wouldn't happen to be the same by any chance?

Ive only been into the campers since June last year, but ive been fiddling with Fiat 850's since 1989, I dont remember though

Tim