Tyre pressures - 205/50/16??
Discussion
Sorry mate, not a tyre I've tried.
The pressure is dependant on the rigidity of the side walls. More rigid = less pressure
There is a way to find out though. Find a undulating and twisty dry road and set your tyres at the book pressures. Drive the road and get a sense of the cars stability. Then pressure up 3 psi and drive it again. If it's worse then try less than book.
In the end the right pressure is the one that suits the way you drive. Asking the collective will only tell you what other people like. I would advise you not to go outside of the range 20 - 26 for normal road driving. 24 - 32 for fast flat track work.
The pressure is dependant on the rigidity of the side walls. More rigid = less pressure
There is a way to find out though. Find a undulating and twisty dry road and set your tyres at the book pressures. Drive the road and get a sense of the cars stability. Then pressure up 3 psi and drive it again. If it's worse then try less than book.
In the end the right pressure is the one that suits the way you drive. Asking the collective will only tell you what other people like. I would advise you not to go outside of the range 20 - 26 for normal road driving. 24 - 32 for fast flat track work.
halfman said:
Hi Shortlad,
Any problems with the 205/50/16 on the front, catching/rubbing etc? Did you have to use a rack stop? Just wondering as I intend to go down the same route as you and put 16's all round. How do the GSD3's feel as this would also be my choice?
Cheers
No problems at all so far. Not had any contact with the wheel and the wheel arch so assume I will be ok. From what I could make out the offset counters the ½" increase in width of wheel.... Don't know if anyone has a comment on that??
I think the main reason is that I stuck with a 205 on the front. This was mainly due to Goodyear not making another size suitable so it had to be the 205/50.
The GSD3's are great as they have very good curb protection built into the tyre.
I like the tyres so far as they seem to grip just as well as the old GSD2's but that's all I have to compare againts.
shortlad said:
Not had any contact with the wheel and the wheel arch so assume I will be ok. From what I could make out the offset counters the ½" increase in width of wheel.... Don't know if anyone has a comment on that??
At the risk of being called pedantic 1/Tyres: you have the same width and the reduction in profile almost matches the increase in wheel dia. as your overall dia. is now 5mm (less than 1%) more so will not be noticable 2/Wheels: I don't know which wheels you have but standard 15" dia. are 7" rims and 1" offset. If you have standard rear wheels on the front then you have put all of the extra rim width on the inside which is not normal practice unless you have a factory where you have run out of 15" wheels, have a lot of 16" wheels and are bringing the product to the end of it's production run, lol. I can't remember whether they put a stop on the steering rack but it's probably easier to fit 5mm spacer plates.
19560 said:
Not had any contact with the wheel and the wheel arch so assume I will be ok. From what I could make out the offset counters the ½" increase in width of wheel.... Don't know if anyone has a comment on that??
At the risk of being called pedantic 1/Tyres: you have the same width and the reduction in profile almost matches the increase in wheel dia. as your overall dia. is now 5mm (less than 1%) more so will not be noticable 2/Wheels: I don't know which wheels you have but standard 15" dia. are 7" rims and 1" offset.
1" ?? ET is 35 on the front and 32 on the rear isn't it..
M@H said:
At the risk of being called pedantic 1/Tyres: you have the same width and the reduction in profile almost matches the increase in wheel dia. as your overall dia. is now 5mm (less than 1%) more so will not be noticable 2/Wheels: I don't know which wheels you have but standard 15" dia. are 7" rims and 1" offset.
1" ?? ET is 35 on the front and 32 on the rear isn't it..
Not as far as I know:-
www.pistonheads.com/gassing/topic.asp?t=174007&f=8&h=0
GreenV8S said:
7" width with 1" inset on the front, 7.5" with 1.25" inset at the back. If you change the width you'll probably need to change the inset too.
19560 said:
As a footnote the natural Griff size appears to me to be 8 x 17 ET30 and run 3mm spacers at the front. (Front original 25mm new 27mm, rear 32mm, new 30mm, all from memory.) Tyres 215/40/17 and 245/40/17. Anywhere close to your musings?
but I think that this is probably the best thread:-
www.pistonheads.com/gassing/topic.asp?t=165710&f=8&h=0
Jonathan
All this talk of offsets and insets is confusing me... not that hard though 
As far as my initial evaluation is concerned the car handles fine with the steering a little sharper which is what I expected due to the reduction in profile.
They also look fine as well but would I be able to see a difference anyway??
The guy that fitted them is a friend and has been in the tyre business for years and he didn't express any concern at what I was doing even though we had a detailed conversation about the offset. It was his theory that the different offset was countered by the ½" increase in wheel width.
Also just to address insets.... I have stuck with the standard factory size for the rears so I don't need to do anything with those.
My main concern is the tyre pressures on the front as I feel that the standard manual setting of 22 may be wrong for the increase in wheel rim size/reduction in tyre wall profile. Is the general rule of thumb to go up in tyre pressure for a reduction in tyre wall size?? Or is there no rules on this one?
As far as my initial evaluation is concerned the car handles fine with the steering a little sharper which is what I expected due to the reduction in profile.
They also look fine as well but would I be able to see a difference anyway??
The guy that fitted them is a friend and has been in the tyre business for years and he didn't express any concern at what I was doing even though we had a detailed conversation about the offset. It was his theory that the different offset was countered by the ½" increase in wheel width.
Also just to address insets.... I have stuck with the standard factory size for the rears so I don't need to do anything with those.
My main concern is the tyre pressures on the front as I feel that the standard manual setting of 22 may be wrong for the increase in wheel rim size/reduction in tyre wall profile. Is the general rule of thumb to go up in tyre pressure for a reduction in tyre wall size?? Or is there no rules on this one?
shortlad said:No the general rule of thumb is to increase pressure if wall rigidity is lower and visa versa. Stay within 20 - 26psi range. Do not be swayed by book settings that were associated with Bridgestone’s. I would ring Goodyear UK Technical Helpdesk: 01902 327070. In my experience these people enjoy discussing these things. Tell them the book pressure, original tyre type and size and ask them how the Eagle GSD3 lines up with regard to rigidity. They'll understand this question and should be able to aim you at an appropriate pressure. I did this when I fitted T1-S's to mine. The fronts are 225/45 16 and I did not agree with TVR's advice. Toyo were happy to advise and I now run 2 psi higher than TVR advised.
Is the general rule of thumb to go up in tyre pressure for a reduction in tyre wall size?? Or is there no rules on this one?
shortlad said:
All this talk of offsets and insets is confusing me... not that hard though
Oh dear.
shortlad said:
As far as my initial evaluation is concerned the car handles fine with the steering a little sharper which is what I expected due to the reduction in profile.
Good, sounds right.
shortlad said:
The guy that fitted them is a friend and has been in the tyre business for years and he didn't express any concern at what I was doing even though we had a detailed conversation about the offset. It was his theory that the different offset was countered by the ½" increase in wheel width.
Depends what he means by countered. You have moved the tyre in and decreased the track and a spacer would counter that, at least in part. It's all a matter of degree/how fussy you are/how fast you drive...
shortlad said:
My main concern is the tyre pressures on the front as I feel that the standard manual setting of 22 may be wrong for the increase in wheel rim size/reduction in tyre wall profile. Is the general rule of thumb to go up in tyre pressure for a reduction in tyre wall size?? Or is there no rules on this one?
I am concerned that you are confused. You've changed the wheel and tyre set up but not drastically. The exact make and model of tyre is going to be much more significant. IMHO take tvrbobs advice and have a chat to Goodyear then post what they say. I chat to G/y, B/stne and Toyo engineers and find them all friendly and helpful.
tvrbob said:
Is the general rule of thumb to go up in tyre pressure for a reduction in tyre wall size?? Or is there no rules on this one?
No the general rule of thumb is to increase pressure if wall rigidity is lower and visa versa. Stay within 20 - 26psi range. Do not be swayed by book settings that were associated with Bridgestone’s. I would ring Goodyear UK Technical Helpdesk: 01902 327070. In my experience these people enjoy discussing these things. Tell them the book pressure, original tyre type and size and ask them how the Eagle GSD3 lines up with regard to rigidity. They'll understand this question and should be able to aim you at an appropriate pressure. I did this when I fitted T1-S's to mine. The fronts are 225/45 16 and I did not agree with TVR's advice. Toyo were happy to advise and I now run 2 psi higher than TVR advised.
Good idea.... D'oh! Why did I not think of that simple solution....
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