Small turning circle with 205 winter tyres

[Bill_56]

It's possible that the Volvo engineers find good technical reasons why different tyres widths benefit form different steering offsets, and so they change the wheel offset to achieve optimum steering for each wheel size.

Another possibility is that the Volvo stylists demand that the 'sightline' down the car should be similar, regardless of wheel fitment, hence the wheel offset needs to be modified to achieve the right 'look', even though it requires the steering offset to be compromised.

If it's the latter, then it would appear that Volvo condone/approve a 6mm reduction in offset when 16 inch wheels are fitted, relative to offset of factory-fitted 17 inch wheels. In which case who knows, the may even condone additional reductions, making it safer to experiments (with Insurers' approval)?

My Haynes manual doesn't seem to mention it so I wonder if anybody with a bootleg copy of Vadis from ebay could confirm whether it includes datasheets that might put actual numbers, or a range of numbers, on the factory steering offsets (as opposed to wheel offsets, which we already know)?

[Jim314]

Could you define 'steering offset'?

[Bill_56]

Originally Posted by Jim314

Could you define 'steering offset'?

I'm not a professional vehicle engineer, and somebody who is may correct me, but my understanding is....

...It is the lateral distance between the centre of the tyre, and the point at which an extrapolation of the steering inclination axis or 'kingping angle' intersects with the road surface.

If the kingpin angle intersects 'outside' the tyre's centre line it is known as 'negative offset', and conversely for positive offset.

[Jim314]

Originally Posted by Bill_56

I'm not a professional vehicle engineer, and somebody who is may correct me, but my understanding is....

...It is the lateral distance between the centre of the tyre, and the point at which an extrapolation of the steering inclination axis or 'kingping angle' intersects with the road surface.

If the kingpin angle intersects 'outside' the tyre's centre line it is known as 'negative offset', and conversely for positive offset.

So there would be a formula which determines 'kingpin angle' using caster, camber, toe. Then another formula using kingpin angle, wheel size and offset (including a spacer if any), and offset due to the dimensions of the hub would give the steering offset. I wonder if Vadis would give that or would it be proprietary?

[Bill_56]

Originally Posted by Jim314

So there would be a formula which determines 'kingpin angle' using caster, camber, toe. Then another formula using kingpin angle, wheel size and offset (including a spacer if any), and offset due to the dimensions of the hub would give the steering offset. I wonder if Vadis would give that or would it be proprietary?

I'm not sure what you mean by the first part of that, as I don't think kingpin angle is directly related to camber or toe.

I've been trying to find a picture and one thing that crops up is my expression 'steering offset' is also known as 'scrub radius'. googling for the latter may yield more hits. Meanwhile, there's a reasonable picture here which illustrates zero-offset as well as describing negative & positive (hope this link works)...

http://moodle.student.cnwl.ac.uk/moo...rubradius.html

Note the above link defined +ve & -ve offset in terms of whether steering axis (also known as kingpin angle) intersects the tyre's midline above or below the road surface, which is different way of describing it, but I think amounts to the same as my own definition.

[Gazdok]

Just to clarify things, this is a picture of where the steering lock limiter would normally be, whether it is white , black or blue.



I took the limiter off COMPLETELY. There is no metal on metal scraping now.
The car's turning circle is miraculously small now.

Yes with 12mm spacers I have redudced my offset with 6.5" wheels to 31mm and with 7.5" wheels to 37mm.
Steering forces do not seem to have increased.
Tramlining is the same as before.

The insurance company was told and they did NOT want to know.

[Jim314]

Originally Posted by Gazdok

Just to clarify things, this is a picture of where the steering lock limiter would normally be, whether it is white , black or blue.



I took the limiter off COMPLETELY. There is no metal on metal scraping now.
The car's turning circle is miraculously small now.

Yes with 12mm spacers I have redudced my offset with 6.5" wheels to 31mm and with 7.5" wheels to 37mm.
Steering forces do not seem to have increased.
Tramlining is the same as before.
The insurance company was told and they did NOT want to know.

Yikes! Why do you think Volvo has a blue color coded limiter pad at that location even with the skinny 195/65-15 tyres on small skinny wheels with a 43 mm offset?

Don't you think that for some good reason Volvo wants the wheels to only turn as far as it can with the peg contacting the thinnest limiter? Don't you think that it is possible that Volvo's reason is that turning the wheels to a sharper angle may cause damage (or at least accelerated wear) to some expensive parts?

My guesses are (1) the steering gear and (2) the outer CV joints.

From my lofty pinnacle of 66 years of age I advise you to put the thinnest steering limiters (blue color coded) back on there.

What wheels and tyres are you using?

[owyn]

Hmmm, this is interesting!
It would be interesting to find out how you go on with a limiter-less setup. I have no doubt there will be a safety device built into the steering rack to stop damaging movement in there.

Please keep us posted on how you go on with regards to feel, handling, tyre wear and any changes in your steering hardware.

the turning circle on these things is atrocious!

[Jim314]

Originally Posted by Gazdok

I have fitted my winter tyres again this week as the weatherman predicts snow. We will probably not get any anyway.

I read on a german Volvo forum that if you fit 205 tyres you can take off the stupid steering lock limiter completely. They were correct!!!!

I did just that and suddenly, for the first time, I would describe the turning circle of our V70 AWD as just that - a turning circle - and not an Orbit.

There is no scraping of tyres, but having said this I am also using 12mm wheel spacers so I can run the fat 225ers with a smaller steering limiter.
I turned full lock and could throw a brick through the gap between wheel and arch.

Volvo have gotten a lot of criticism for their large turning circle. I owned a 1996 base model 855 (i.e., an 850 wagon with I think 195/60-15 tyres on steel wheels) and now own a 2004 V70 with the blue steering limiter and 195/65-15 tyres on Saurus alloy wheels. I think the turning circle of the '04 V70 is significantly larger than that of the '96 850. Irritatingly and inconveniently larger!

But since Volvo always got a lot of criticism for this I have always assumed that Volvo must have had a reason for this. I have always assumed that Volvo accepted this deficiency in order to achieve other goals like reduced cost, increased safety . . .

Your experience has made me wonder how Volvo arrived at the specifications for the steering limiter pads.

Does this German Volvo site you reference cater to those with reasonably cautious opinions or would one find advocates of reckless tinkering to, for example, give a Volvo the same turning circle as that of a BMW or a Mercedes?