Classic Alfa Forums

I’ve decided that I should let my set of (5) Ti steels go to a new home. These are the desirable 5.5 J x 13 steel wheels fitted to Tis and sprints. These are becoming almost impossible to find these days which is why I thought I’d never let them go. But the truth is my cars on a Rottiserie and when it comes off it’ll go on to it’s 14” Revolutions. Or the 14” pepperpots. My Suds a S3 so they’re not correct anyway but I always just liked the look of them for a steel wheel I think they’re awesome. I’ll be posting them on EBay within the next few days unless a,forum member wants to grab them first. I’ve been in the attic and dug out the centre caps.
I’m in no rush to sell and would like them to go to a good home and I would consider other Sud bits in part trade etc the tyres all hold air (I think they've got tubes in ???). but they’re over 25 yo so the tyres are basically scrap I was just using them as “Roller” wheels. I’m asking £375 for all 5 with 4 caps. I feel that’s reasonable given that they are becoming hard to find these days. A chap in Edinburgh wants 200 for a single one ??
Pt ex considered W. H.Y ??
Lou

Hi Lou, can I ask if the 185/60 profile gives the same sort of rolling radius as the original spec 165/70 's.
Namely, does the speedometer still read accurate ?
Cheers.

I can’t remember to be honest Keith but I don’t think it made a massive difference

It's easy enough to work out:

Wheels are 13" diameter, so I convert the tyre width (e.g. 165mm) to inches (divide by 25.4), multiply by 0.7 (70%) to get the sidewall height, multiply by two and add to the wheel diameter to get the circumference (in inches).

Or you can convert the wheel diameter into mm and do it all in Roman Catholic

To look at the difference in speed calibration, multiply the diameter of the wheel and tyre by Pi to get the circumference. This is the distance traveled by the wheel in a single revolution. The difference between the two, expressed as a percentage, is effectively the error introduced by the new wheel and tyre combination.

To summarise then:

185/25.4 = 7.28 inches (tyre width)
7.28 x (60/100) = 4.37 inches (sidewall height)
4.37 x 2 + 13 = 21.74 inches (wheel and tyre diameter)
21.74 x Pi = 68.3 inches circumference

The same formula applied to a 165/70 tyre gives a circumference of 69.4 inches, a difference of -1.1 inches

-1.1/68.3 x 100 = -1.63%

This shows the difference to be 1.63% optimistic, so not only well within the legal limit for speedometer accuracy (10%, assuming the speedo is accurately calibrated in the first place) but staying on the right side of the law at the indicated speed limit

I tried several other combinations of tyre width and profile (175, 195, 65 and 55%), but 185/60 is pretty much the optimum combination of width and profile for this wheel. Which is of course why Lou choose it

Lauren

I'm being a techno-nerd again, aren't I?

Correct Lauren. Of course that formula is exactly what I was thinking. I just summarised with “I don’t think it made a massive difference”. LOL

Cheers Lauren, thanks for that, as Lou says then.

LooLooSud33Spider wrote: ↑

Sat Aug 27, 2022 9:05 pm

Correct Lauren. Of course that formula is exactly what I was thinking. I just summarised with “I don’t think it made a massive difference”. LOL

Point taken - I'll shut up now

or just use an online tyre size converter

https://alloywheels.com/tyreCalculatorResults2

also has the negative effect of a heavier steering effort needed for parking mind