Macbeast
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| posted on 8/4/13 at 09:27 AM |
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Tyre Pressures
Got 185/65/R14 on all four wheels and, following advice on here have set pressures to 18 psi
I found yesterday that at about 70mph the car was weaving a bit and it felt like an oscillation could build up.
I think the sidewalls of a tyre designed for 26 psi could be flexing and I can certainly wobble the car sideways ( at rest  ) Wouldn't it be
better to increase the pressure and to what ?
As in post last week, I'd like slimmer tyres anyway. Would a 165 x 75 x 14 stay on a 5.5 J rim or would I need to change the rims too ?
[Edited on 8/4/13 by Macbeast]
I'm addicted to brake fluid, but I can stop anytime.
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edsco
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| posted on 8/4/13 at 09:51 AM |
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Several factors to consider:
1. What make model of tyre you have?
2. Is it that your just using the car for a spirited drive or track work?
For racing i tend to opt for circa 17-18psi purely because when racing the pressures rise alot so as long as you get the tyres up to temp quickly its
fine otherwise its like driving on ice. Ideal operating temp for a A048r is 21psi on track so i am told.
Road going....on the same tyre might want to start at 21psi as you wont get the heat in them in the same way.
If the tyre is just a normal road tyre i.e. Pirelli or something similar.....coz your car is invariably going to be lighter than a normal tin top
i'd go higher. like you say 26-28psi.
Its trial and error....add a bit more until you are happy with the end result.
edsco
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Macbeast
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| posted on 8/4/13 at 10:04 AM |
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Thanks
It's just for pottering about and with motorway 70 ish to shows etc.
No motorsport pretensions
I'm addicted to brake fluid, but I can stop anytime.
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Macbeast
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| posted on 8/4/13 at 11:13 AM |
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Just thought " motorsport pretensions " could be misinterpreted. I wasn't being snide about people who enjoy motorsport: I just
meant I'm too old and too timid to take part myself
I'm addicted to brake fluid, but I can stop anytime.
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edsco
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| posted on 8/4/13 at 11:18 AM |
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No misinterpretation here.....too old and timid is what i thought you meant!!! lol
edsco
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bi22le
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| posted on 8/4/13 at 11:38 AM |
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I think 18psi is too low for general road use and expects alot of heat and energy to be put in which will increase PSI. If your not doing this then
maybe add pressure as stated.
For reference I have 2 sets of wheels. R888 for track I set at around 18PSI. Faulkner (SP?) road tyres are at 25PSI for increased MPG and feel.
Somebody will be along shortly to give a more experienced answer. For me 18PSI is too low for road use.
Track days ARE the best thing since sliced bread, until I get a supercharger that is!
Please read my ring story:
http://www.locostbuilders.co.uk/forum/13/viewthread.php?tid=139152&page=1
Me doing a sub 56sec lap around Brands Indy. I need a geo set up! http://www.youtube.com/watch?v=EHksfvIGB3I
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Macbeast
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| posted on 22/4/13 at 08:29 AM |
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Well, I've gone from 185/65/R14 to 165/82/R13 on the front ( giving the same diameter ) and the drive is much nicer. The steering is lighter and
with 24 psi I don't get the same ominous feeling of impending oscillation. The only negative is that the cycle wings are no longer symmetrical
over the tyres so a bit of strut bending is called for
I'm addicted to brake fluid, but I can stop anytime.
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