Rims & tyres

[Oversize]

Scratch that, seems you already hinted to a big yes! In what way was it better??

 

[BAR]

Forget the calculator: just drop into this web page:

http://www.exploroz.com/Vehicle/Tyres/SizeCalc.aspx

 

[SEL_69L]

Just make sure that you have the right offset for the wheel you choose, if you are going to change them. With the front wheels, the axis of the kingpin should pass through the centre of the tyre contact patch on the road.

The higher the aspect ratio the more compliance the tyre has, and can offer to keep the tyre in contact with the road but can lead to more case distortion with hard cornering. Obviously, a trade off, and helps you understand where you are in the ride / roadholding compromise.

Larger diameter and wider wheels, although they look better to some folks, tend to be heavier, and can lead to greater unsprung weight, which leads to more work for the suspension and a harder life for suspension bushings.

 

[Styria]

There is no doubt that these Speedy rims weigh the proverbial 'ton' - honestly, picking one up and fitting it is quite an exercise. Chances are that the suspension has to work harder on account of the greatly increased unsprung weight, but I am prepared to accept that for the sake of, dare I say it, better looks and, in my view, superior road handling and road feel. Regards Styria

 

[SEL_69L]

Superior handling and road feel is, in my humble opinion, a resultant combination of the ability of the suspension to do it's work and the result skill of the tyre manufacturer to make his procuct perform to the customer's required expectations.

 

[Oversize]

Styria I'd check the load ratings on your tyres, as the Tyre and Rim Association Standards Manual (2011) suggests a 235/40R18 has a maximum load rating of only 95. The minimum is 97 on a 6.9. However I have found that the load rating for a particular size can vary between brands and it all comes down to sidewall construction. Some tyres are marked 'XL' which indicates they can accomodate 'Extra Load'.

I'm headed towards some 18s on one of my cars and I will probably look at 235/45R18 for the front, which has a slightly higher profile (still within 15mm of the standard OD), holds more air and therefore has a load rating of up to 98 (Kumhos).

On the rear I'm looking at 255/40R18. Yes they have a lower profile than those at the front, but are still within 15mm of the standard OD to keep the speedo accurate. A lower profile on the rear is common, even on standard cars and usually corresponds with wider tyres. Having the opposite (lower profile on the front) can upset handling and induce additional oversteer which is hard to control. Hence it's a no-no on anything post 1949.

 

[Oversize]

I am not fully conversant with the limits imposed by body width and suspension components that may be affected by excessive tyre/rim width. I do know that 2.35.40.18s fit quite comfortable, and I think the rims are eight inches wide - I should really go and measure the width, shouldn't I ? Well.....

As you may be aware, I have refitted the standard size 14" Bundts to the rear of Gleaming Beauty, with 2.25.65.14" Toyo Tyres, but I am still running the 'fancy' Speedy rims with the 18"ers on the front. To say the handling is 'different' is an understatement.

Traction in the wet, at the rear, is chancy at best. We have had a bit of rain in Sydney during the last couple of days, and I have come to treat the road surface, when wet, as a bit of an ice rink. Seriously, I could turn this thing around (Gleaming Beauty) 180 degrees in the twinkling of an eye lid. In the dry, the 'chirping' of tyres is very easily accomplished - not that I am all that impressed by that. Admittedly, the Toyos aren't all that new (still plenty of tread, though), but the difference in handling capabilities and safety between the aftermarket set-up and "original" (perhaps XWXs excepted) is remarkable. Presently, I am waiting for the second new spare rim (as illustrated in earlier posts) to be ready for pick-up and once new Nankangs are fitted, that should restore the safe and capable handling. Regards Styria

Styria the VSBs only allow the profiles of front and rear tyres to vary by no more than 10, due to handling issues. Fitment as described above varies by 25 and this confirms why you have traction issues....

 

[Oversize]

Oh I found it (this thread)! I've heard that using a wheel offset of anything other than e30 on a W116 can have detrimental effects on the handling characteristics. And this includes AMG specified Pentas (and any other wheel) with offsets such as e11, or e17. This is due to the zero scrub radius design of the front suspension/steering.

Styria have you experienced any issues using the Speedy wheels? As I asked in the other thread, do you know the width and offset of your wheels?

 

[motec 6.9]

Hi Mark that is correct about offset my 17 inch wheels on old car were et25 .They were 7.5 inches wide . My AMG Pentas are 16x8 with et11 . When talking to Simmons they have sold to W116/W126 owners thet have et specs on file said et18 for 10 inch wide rear fits . http://www.topklasse.org/forums/showthread.php?t=3721 this may help as sellers in Germany must post et of wheels . Geoff