froggy
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| posted on 28/3/16 at 10:37 AM |
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Spring rate for a heavy wheel/tyre combo ??
First few drives have been a bit choppy to say the least and the rear shocks have what I'm pretty sure are 150 lb springs but the wheel/ tyre
combo is a lot heavier than it should be so mulling over which way to go as its ride quality I'm after rather than ninja handling .
Steel 10" wide rim with a 255/50/16 tyre
Ordered a pair of 100lb springs to start with and assembling bits to make a 1/2 arb for the rear . Tried a few shock settings but it feels like
it's just a bad sprung / unsprung ratio
Camber is 0.5 neg and the chassis is square with 15 min toe equal across the rear axle . Pressure is down to 15 psi which improved the ride and the
tyre doesn't look under inflated or hot at the edges after a run . The tyres are old but in good shape
There is a 20mm spacer on the rear for clearance but the wheels are Citroen c5 steels so even with the 3" band the centre offset is still well
in the range of a normal et for this type of car .
[IMG]http://i144.photobucket.com/albums/r187/froggy_0[IMG]
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froggy
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| posted on 28/3/16 at 10:40 AM |
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Changing wheels isn't an option until every other avenue is exhausted
[IMG]http://i144.photobucket.com/albums/r187/froggy_0[IMG]
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Ugg10
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| posted on 28/3/16 at 10:44 AM |
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Are the shocks adjustable, if so what are they set at, should be near the bottom of the range iirc my Gaz one are 6 clicks out of about 40. If the
shocks are too rigid this may give the same impression as too stiff springs.
---------------------------------------------------------------
1968 Ford Anglia 105e, 1.7 Zetec SE, Mk2 Escort Workd Cup front end, 5 link rear
Build Blog - http://Anglia1968.weebly.com
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froggy
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| posted on 28/3/16 at 10:50 AM |
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Protech adjustables and tried various settings but the only real difference has been lowering the tyre pressure
[IMG]http://i144.photobucket.com/albums/r187/froggy_0[IMG]
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ian locostzx9rc2
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| posted on 28/3/16 at 11:12 AM |
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I would have thought 150 or 100lbs springs are to low I would think 180lbs or 200lbs springs would be better and check the shocks are ok do you need a
shock with more movement?
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froggy
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| posted on 28/3/16 at 11:22 AM |
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I need to weigh the wheel properly but it's a lot heavier than the front and my fuel tanks are in front of the rear axle so no weight behind the
axle
[IMG]http://i144.photobucket.com/albums/r187/froggy_0[IMG]
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Mr Whippy
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| posted on 28/3/16 at 11:24 AM |
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look at the dirt on the back tyre tread, your tyre pressure is way to high as the outer tread isn't even touching the ground. The back end on
that must be very light.
They way I use to do it was to clean the tyre and roll it over a dusty floor and see at what point the edge of the tread began to stay clean then
lowered it a few psi from that point. I had this especially with my beach buggy which turned out to need just 15psi, after that the tyre wear, road
holding & ride were great.
[Edited on 28/3/16 by Mr Whippy]
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froggy
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| posted on 28/3/16 at 11:35 AM |
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That is at 15 psi but being big and having very little weight it might need to cone down even more . top tip there mr whippy cheers
[IMG]http://i144.photobucket.com/albums/r187/froggy_0[IMG]
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roadrunner
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| posted on 29/3/16 at 08:58 AM |
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Sounds like you might have run out of travel with the shock length. Have you tried lowering the ride height.
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britishtrident
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| posted on 29/3/16 at 09:01 AM |
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For best ride the wheel rate should be softer at the front than at the rear, in technical terms the frequency of the suspension should be lower at the
rear. This reduces the bucking bronco effect.
To compensate for the reduction in roll stiffness at the front a front anti-roll bar is used to balance handling.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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froggy
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| posted on 29/3/16 at 10:52 AM |
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Rear shock is set with 60/40 bump- droop at current ride height . Weighed the rear wheel compared to the 0z 7x15 with 195/50/15 and it's 3 times
the weight so a huge difference is unsprung weight , il get someone to follow me and film it to see what's going on but some feedback on the hot
rod forums suggest I might get as low as 10psi to get the tyre in full contact with the road
[IMG]http://i144.photobucket.com/albums/r187/froggy_0[IMG]
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MikeRJ
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| posted on 29/3/16 at 02:20 PM |
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Getting suspension with a poor sprung/unsprung weight ratio to work as well as it can is more about damping than spring rate.
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froggy
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| posted on 29/3/16 at 02:41 PM |
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Il weigh it in my brake rollers to get an accurate axle weight to get a better idea of th actual axle weight compared to the rough unsprung weight .
Softer springs should help as it will affect the re bound damping to some degree .
[IMG]http://i144.photobucket.com/albums/r187/froggy_0[IMG]
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Rob Allison
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| posted on 2/4/16 at 01:44 PM |
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Just a thought for you.
apart from springs and dampers. The 255/60r16 on a 10" rim is stretched by about 1". The tyre is rated for 8 to 9" rim width. ok it
doesnt look stretched but it doesnt take much to load the trye wall up with a stretched tyre. So it may be it just transmitting the shock load harder
through the tyre wall.
Is there any other wheels you can try to check this.
Also how old are the tyres?
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froggy
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| posted on 2/4/16 at 03:37 PM |
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I looked at my build thread on another forum and I put the tyres on three years ago after getting the rims banded and the only ones I could get hold
of where from a tyre shop next door to my garage , I had the idea that having the tyre a bit snug on the rim might make it a bit stiffer but that was
a few years back .
After looking at the date code which turned out to be pre 2000 style and these were made mid nineties . They were free and just to get the car rolling
so no great loss and they'll come in handy if I run out of the stock of part worns I've got .
Just out of curiosity I took the valves out to see how stiff they are were still up with nothing in them
Getting them off at work was a bit of a maul for a 50 series and once off the first 50mm of sidewalk is like a bm run flat !!!
Put some kuhmo ecsta dated 2006 and with 10psi in they feel much more like a tyre now
That aside its not uncommon for rods with largish rear tyre to run under 10 psi so I'm still going to try the 100lb springs and go from there as
its still a very heavy Lump bouncing around
[IMG]http://i144.photobucket.com/albums/r187/froggy_0[IMG]
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froggy
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| posted on 5/4/16 at 09:42 PM |
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Softer springs didn't work so tried some 250lb that I had and the ride is transformed . Tyre pressures are now up to 18 rear and it feels very 7
like with the rear moving around nicely with a bit of lift off oversteer
[IMG]http://i144.photobucket.com/albums/r187/froggy_0[IMG]
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phelpsa
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| posted on 5/4/16 at 10:29 PM |
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It's an interesting topic, something I haven't really thought about since uni! The car looks perfect by the way, I've always loved
that style.
I'd hazard a guess that the dampers are a bit stiff in low speed and soft in high speed, so the unsprung mass is under damped and sprung is over
damped. If you're under damped at certain natural frequencies then you'll really feel it, but go a bit stiffer an you move out of the
sensitive frequencies. Hence stiffer springs = more comfort.
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froggy
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| posted on 6/4/16 at 09:23 AM |
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I've been driving a mid engined car for the last five years so it's a joy going sideways with no drama
[IMG]http://i144.photobucket.com/albums/r187/froggy_0[IMG]
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Nickp
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| posted on 6/4/16 at 11:39 AM |
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quote:
Originally posted by froggy
Softer springs didn't work so tried some 250lb that I had and the ride is transformed . Tyre pressures are now up to 18 rear and it feels very 7
like with the rear moving around nicely with a bit of lift off oversteer
So, it's ready for Monaco now?? 
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froggy
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| posted on 6/4/16 at 12:51 PM |
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The bits with Toyota written in are behaving very well that's all I'm saying
[IMG]http://i144.photobucket.com/albums/r187/froggy_0[IMG]
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Nickp
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| posted on 6/4/16 at 01:04 PM |
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quote:
Originally posted by froggy
The bits with Toyota written in are behaving very well that's all I'm saying
And the bits with 'Froggy built' less so??
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froggy
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| posted on 6/4/16 at 02:08 PM |
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Just remember I don't wear pyjamas and I've bagsied the big spoon
[IMG]http://i144.photobucket.com/albums/r187/froggy_0[IMG]
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ian locostzx9rc2
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| posted on 6/4/16 at 02:20 PM |
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Glad u got it sorted
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Nickp
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| posted on 6/4/16 at 02:23 PM |
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quote:
Originally posted by ian locostzx9rc2
Glad u got it sorted
Spring rates or spooning?? 
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