That's tight... Powerflex fitted to top arm
Discussion
Okay.. so just fitted the first arm having fit Powerfex to the wish bones... Removed the paint from the bore as instructed.. pushed them home with a G clamp.. Lubricated everything.. opened the mounts on the Cassis a bit to get them in... located them in position using a screw driver down the bore etc... tapped home the bolt... and done up to 40 LBS/FT..... nice.. took about 1 hour all in....
But it's very tight.. smooth yes.. but tight... Put it this way... with one hand / arm I can only just move it... is this right?..
Sure it will be as I could not have done it any other way but blimey... I know the forces here are huge on the suspention.. and I'm sure it will soon free up... but did anyone else notice this?..
As tight as a gnat's..
cheers
Edited by TVR Beaver on Saturday 18th December 21:00
For a start, you shouldn't tighten up the bolts until the suspension is loaded. i.e. the car is back on its wheels or axle stands under the hubs.
The other point is 40lb/ft may be too tight as this is a dry torque value. If the bolt is lubricated, the torque must be reduced by around 25% - see the warning note on all my bolt kits.
And yes they can be as you described.
The other point is 40lb/ft may be too tight as this is a dry torque value. If the bolt is lubricated, the torque must be reduced by around 25% - see the warning note on all my bolt kits.
And yes they can be as you described.
Cheers Guy's.. but why only when it's loaded / on it's wheels?.. the bolts are a good fit in the middle tubes so no movement to take up there... and it's now a bearing (kind off).. not like locking the rubber units up so they become stressed at normal sitting position.... but I guess it's to take up 'any other' slack in the system .. but don't think there is any but will re-do when on it's wheels anyway....
And the torque on the bolts are 45/50 LBS so at 40 I've reduce it about 25% or so....
Good to hear it's correct anyway... I did think it was very tight but I'm sure not as tight as the rubber units (no experiance with these)...
It does all work nice until you torque it up and then the thrust washers are pushed up hard against the inner's.. that's when it becomes stiff but you must do this and lock the tube, otherwise it will be the tube on the bolt thats the bearing...
.
Also.. It does become apparent when doing this that the arms are may be not as accurate as they might be!.. one of the ends needed the bolt hammering a tad to get it into the second half of the mount.. Indicating it's twisted a tad (on initial welding I assume)... So these things don't help!!...
And the torque on the bolts are 45/50 LBS so at 40 I've reduce it about 25% or so....
Good to hear it's correct anyway... I did think it was very tight but I'm sure not as tight as the rubber units (no experiance with these)...
It does all work nice until you torque it up and then the thrust washers are pushed up hard against the inner's.. that's when it becomes stiff but you must do this and lock the tube, otherwise it will be the tube on the bolt thats the bearing...
.
Also.. It does become apparent when doing this that the arms are may be not as accurate as they might be!.. one of the ends needed the bolt hammering a tad to get it into the second half of the mount.. Indicating it's twisted a tad (on initial welding I assume)... So these things don't help!!...
Edited by TVR Beaver on Sunday 19th December 08:32
When I did my powerflex bushes last year I didn't experience this level of tightness in the arms, yes they were firm but could be moved freely up and down with relative ease. I also dont understand why the bolts should be torqued when the suspension is loaded as the powerflex bushes are a bearing and should have free movement with no middle load point needed like the solid rubber ones. If the arms are so tight at 40lb torque that you struggle moving the arms up and down I would think that there is something wrong.
Chris
Edit to say that I am not sugesting anything anyone else has said is wrong but would be interested to find out why the bolts should be torqued on these bushes with suspension loaded. Also I guess every TVR is different and just because mine was not that stiff doens't necessarily mean that Johns is wrong.
Chris
Edit to say that I am not sugesting anything anyone else has said is wrong but would be interested to find out why the bolts should be torqued on these bushes with suspension loaded. Also I guess every TVR is different and just because mine was not that stiff doens't necessarily mean that Johns is wrong.
Edited by chris52 on Sunday 19th December 08:53
They're bushes they distort & it works best for you when preloaded.
All bearings have some resistance, the thrust on the ends of the suspension bushes where they get clamped does stiffen them up.. Since they only cycle within a limited arc this is effectively just a factor you use in tuning the suspension, it's fairly insignificant compared to the swinging dead weight of the unsprung loads IMHO.
All bearings have some resistance, the thrust on the ends of the suspension bushes where they get clamped does stiffen them up.. Since they only cycle within a limited arc this is effectively just a factor you use in tuning the suspension, it's fairly insignificant compared to the swinging dead weight of the unsprung loads IMHO.
spend said:
They're bushes they distort & it works best for you when preloaded.
All bearings have some resistance, the thrust on the ends of the suspension bushes where they get clamped does stiffen them up.. Since they only cycle within a limited arc this is effectively just a factor you use in tuning the suspension, it's fairly insignificant compared to the swinging dead weight of the unsprung loads IMHO.
I'm sure this is true... but I'd bet you could hang the hub and caliper from the top one and it would only just move... and you know how heavy they are!! (equates to about the same using my 'comparison' measuring units as I guess you could just about lift the hub and caliper with one hand / arm All bearings have some resistance, the thrust on the ends of the suspension bushes where they get clamped does stiffen them up.. Since they only cycle within a limited arc this is effectively just a factor you use in tuning the suspension, it's fairly insignificant compared to the swinging dead weight of the unsprung loads IMHO.
)Just didn't expect them to be so tight... I'm sure they will get looser in use... But you must be at risk of spinning the bush assy in the Arm tube especialy if you've used lube when pressing them in??...
Quinny said:
When I did mine, the wishbone, would just about stay where it rested, but just a small amount of force, would lift or lower it as required
By the way I fitted the bottom one first, then the shock, then the hub, and finally the top wishbone....
Seemed a logical way of putting it back together...
Mine was the same as yours and after a little digging on google I found this from a company called smartracing By the way I fitted the bottom one first, then the shock, then the hub, and finally the top wishbone....
Seemed a logical way of putting it back together...
Edited by Quinny on Sunday 19th December 16:38
This is a extract from them on how to fit urethene bushes
5) Fit Definition: The fit is correct when the suspension parts can be moved with very little effort when
moved by hand - let's say less than 5 ft-lbs of torque. It's almost better to have the fit be just a bit loose
than it is too tight.
6) Fitting Sequence: Press the bushing into whatever housing it will be in, ie, torsion housing, spring plate
cap or front arm housings. If it fits just snugly, leave it, if you have to jam it in with a hammer or press,
adjust the shape or dimensions until it fits just snugly - this is important because if you don't fit the OD
first, the ID will change when installed. Then fit the ID until the fit is correct. In the rear or spring plate
area (without the torsion bar installed), you want to be able to grab the spring plate and move it up and
down without herniating yourself - it should be snug, but not hard to move. The fronts should be pressed
into the front and rear housings and then the ID adjusted. When the arms are reinstalled on the car, the
arms should swing up and down with little effort of one hand. Shims may be needed to get proper
alignment of the A-arms; they can be added to the front mount of the A-arm. Be sure to liberally
lubricate the bushing prior to final assembly.
FYI: If you've ever installed a set of bushings that did not fit correctly and were forced in place and then tried to
corner weight the car and could not get the car to duplicate its readings, poor bushing fitting is often the reason."
Chris
Quinny said:
When I did mine, the wishbone, would just about stay where it rested, but just a small amount of force, would lift or lower it as required
By the way I fitted the bottom one first, then the shock, then the hub, and finally the top wishbone....
Seemed a logical way of putting it back together...
Chris came down last night and had a look and confirmed what I thought... Far too tight... if you get the lower one doing the same thing I'm sure it would be a problem... Will call SH today and see what he can suggest...By the way I fitted the bottom one first, then the shock, then the hub, and finally the top wishbone....
Seemed a logical way of putting it back together...
Edited by Quinny on Sunday 19th December 16:38
TVR Beaver said:
Quinny said:
When I did mine, the wishbone, would just about stay where it rested, but just a small amount of force, would lift or lower it as required
By the way I fitted the bottom one first, then the shock, then the hub, and finally the top wishbone....
Seemed a logical way of putting it back together...
Chris came down last night and had a look and confirmed what I thought... Far too tight... if you get the lower one doing the same thing I'm sure it would be a problem... Will call SH today and see what he can suggest...By the way I fitted the bottom one first, then the shock, then the hub, and finally the top wishbone....
Seemed a logical way of putting it back together...
Edited by Quinny on Sunday 19th December 16:38
Chris
I think the tightness is due to the bolts being tightened without any load and that the bolt torque is clamping the thrust washers in place so that these are causing the tightness. It may be compounded by the new powdercoating making the arms thicker than normal.
I would remove the bolts and arm and refit. I would spread the chassis plates a little so that there is no clamping and put the wishbone back in.
I also think the 40lbft torque may be a little too high. 45lb less 25% is 33.75 lb ft. Add the fact that torque wrenches can be inaccurate and the tightness could be down to overtightening. The actual bolt torque could be nearer 60lbft and that is way too high and trapped the arm between the chassis plates.
I never tighten the bolts up until the car is back on its suspension. This ensures that everything settles into place rather than be forced.
I would remove the bolts and arm and refit. I would spread the chassis plates a little so that there is no clamping and put the wishbone back in.
I also think the 40lbft torque may be a little too high. 45lb less 25% is 33.75 lb ft. Add the fact that torque wrenches can be inaccurate and the tightness could be down to overtightening. The actual bolt torque could be nearer 60lbft and that is way too high and trapped the arm between the chassis plates.
I never tighten the bolts up until the car is back on its suspension. This ensures that everything settles into place rather than be forced.
Bushes are okay.... and I will torque up when supported on the hub's so any slack in the system is in it's natural position...
Will have another play this week and may be tweek a few of the bushes / washers to get a better fit and a lower clamping force...
.
All that said, when you think how hard it is to pull out a shock absorber with your hands in comparison with the way they shoot up and down when in use.... am I being a bit OTT here... Does it realy impact the end result that much?... anyway.. for my own statifaction I'll get them all the same and smooth ..
Will have another play this week and may be tweek a few of the bushes / washers to get a better fit and a lower clamping force...
.
All that said, when you think how hard it is to pull out a shock absorber with your hands in comparison with the way they shoot up and down when in use.... am I being a bit OTT here... Does it realy impact the end result that much?... anyway.. for my own statifaction I'll get them all the same and smooth ..
spend said:
Try blowing a fan heater / hot air gun around the bushes to check if its just a case of super cold induced stiffness.
We are in a rather unusual situation at the moment
Indeed... The only super cold stiff thing in the garage is me We are in a rather unusual situation at the moment
I did try that and it made little difo.... 
Well, the front end is done... But I've played about a lot with them and got them to how I think they should be?... Need to call Powerflex really but they wont be open till next year may be??..
.
Anyway.. I've basicaly ended up taking about 1.2mm of the bush assy to get them nice...
If you put the metal bearings in the PU bush and put two together and measure the length, they were coming out at about 44.5 / 44.7mm... when you push the bush units in the arm tube, due to them being squeezed they got longer by about .5mm, so ended up around 45.6 mm on average.
The tube lengths on the arm are about 44mm dead on, so what I've done is taken 1.2mm off the length of one of the bushes to make them flush with the tube ends when fitted.
The inner tube that creates the bearing is about 50mm long and the thrust washers 3.1 mm wide... so when you put it all together and nip it up, you get about .2mm compression.. this gives a nice movable arm that will move without too much effort... but will still hold a 3 LBS lump hammer without falling...
Before it was a two handed job to move them and I'm sure that was too tight....
Just hoping now that you don't need a certain amount of comression to make them work propperly and that I don't have things floating about within 1000 miles or so
If this does happen I can insert a 1mm shim into one side of the assy to basicaly get me back to where it started... but let's see what happens?....
Question is... do I do the same on the rear now??
.
Anyway.. I've basicaly ended up taking about 1.2mm of the bush assy to get them nice...
If you put the metal bearings in the PU bush and put two together and measure the length, they were coming out at about 44.5 / 44.7mm... when you push the bush units in the arm tube, due to them being squeezed they got longer by about .5mm, so ended up around 45.6 mm on average.
The tube lengths on the arm are about 44mm dead on, so what I've done is taken 1.2mm off the length of one of the bushes to make them flush with the tube ends when fitted.
The inner tube that creates the bearing is about 50mm long and the thrust washers 3.1 mm wide... so when you put it all together and nip it up, you get about .2mm compression.. this gives a nice movable arm that will move without too much effort... but will still hold a 3 LBS lump hammer without falling...
Before it was a two handed job to move them and I'm sure that was too tight....
Just hoping now that you don't need a certain amount of comression to make them work propperly and that I don't have things floating about within 1000 miles or so
If this does happen I can insert a 1mm shim into one side of the assy to basicaly get me back to where it started... but let's see what happens?....
Question is... do I do the same on the rear now??
I've just checked with several new bushes out of some packets on the shelf and the overall bush width is dead on 44mm when the two halves are assembled together.
I have assembled a bush and measured it and it comes up exactly with the 44mm/50mm dimensions you mention.
This seems to indicate that either the bushes you have are longer than they should be or that when they are inserted into wishbone tube, they are not coming together in the centre and there is a gap. This could mean that something in the powder coating that is causing a problem.
I am a bit concerned that when the bush was inserted it elongated the bush as much as it has done as this does indicate that the clearance inside the wishbone tube is less than it should be - it could be the powder coating is thicker than normal. This would also stack up with the two halves not meeting fully as the bushes may be elongating at both ends. The biggest effect is from the bush elongation so if this had not happened then I suspect that the tightness would not be there.
There are some 102's used in the rear wishbones - it would be worth checking to see what dimensions they are before fitting. If they are 44/50mm then I think the problem lies in the powdercoating thickness rather than an out of spec bush.
The main concern I would have is any deformation caused by the elongation and whether this has now created an oval bearing which will wear quicker.
I'll discuss this with Powerflex in the New Year.
I have assembled a bush and measured it and it comes up exactly with the 44mm/50mm dimensions you mention.
This seems to indicate that either the bushes you have are longer than they should be or that when they are inserted into wishbone tube, they are not coming together in the centre and there is a gap. This could mean that something in the powder coating that is causing a problem.
I am a bit concerned that when the bush was inserted it elongated the bush as much as it has done as this does indicate that the clearance inside the wishbone tube is less than it should be - it could be the powder coating is thicker than normal. This would also stack up with the two halves not meeting fully as the bushes may be elongating at both ends. The biggest effect is from the bush elongation so if this had not happened then I suspect that the tightness would not be there.
There are some 102's used in the rear wishbones - it would be worth checking to see what dimensions they are before fitting. If they are 44/50mm then I think the problem lies in the powdercoating thickness rather than an out of spec bush.
The main concern I would have is any deformation caused by the elongation and whether this has now created an oval bearing which will wear quicker.
I'll discuss this with Powerflex in the New Year.
Edited by shpub on Monday 27th December 16:53
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