DonDP Posted March 31, 2019 Author Share Posted March 31, 2019 Thanks guys, the lsd was new/rebuilt 1500 miles ago so whilst on my list as a suspect I am hoping its unlikely. The vibration is hugely reduced and possibly stops off throttle. Which to me would now rule out wheels/tyres.On a separate thread about the propshaft play, ‘Jim 123’ noticed that one of the circlips on the propshaft is bent/non standard, so something has gone on with it in the past. I have ordered a new propshaft and will be replacing it next week now.Hopefully this will resolve the issue but a good shout to check the CV joints on the drive shafts too. I have been turning the rear wheels by hand and everything seems smooth but will remove the CV boots and inspect while I am doing the propshaft. Link to comment Share on other sites More sharing options...
DonDP Posted April 9, 2019 Author Share Posted April 9, 2019 UPDATEI put a new prop shaft in but the problem persists....I decided to pop the car up on some jack stands (make sure it was really secure), remove wheels, started it and popped it in 4th gear at idle speed to see if there was anything that looked like it could cause the high speed vibration.I may have found the culprit. See here : looks as though it is the disc that is warped, which is odd as you can't feel this through the pedal, but at 100mph+ I think it could certainly be the source of the vibration.Question is, do you think it is just the disc or could it be more? Link to comment Share on other sites More sharing options...
Jim 123 Posted April 9, 2019 Share Posted April 9, 2019 Maybe get a dial gauge on both the disc rotor and the hub face? Link to comment Share on other sites More sharing options...
revilla Posted April 9, 2019 Share Posted April 9, 2019 Link: Maybe it's just an illusion with the frame rate of the video but the in/out movement of the disk looks to be slower than the rate of rotation.There isn't any play in the wheel bearing is there, allowing the whole hub to move? Wht happens if you grasp the disk on both sides and push and pull? Link to comment Share on other sites More sharing options...
DonDP Posted April 10, 2019 Author Share Posted April 10, 2019 @Jim123 - agreed, dial gauge as a next step to see just what is out of true. Just need to acquire one...@Revilla - I think it’s an illusion. There is absolutely no play in there but doesn’t mean something else a bit fishy might be going on with the bearing/hub/driveshaft...I just hope this is getting to the bottom of it. Will be a couple weeks now until I get to check with a dial gauge but will keep this thread updated when I do. Link to comment Share on other sites More sharing options...
ChrisC Posted April 10, 2019 Share Posted April 10, 2019 Given the price of rear disc, I think I would just replace them. Link to comment Share on other sites More sharing options...
DonDP Posted April 10, 2019 Author Share Posted April 10, 2019 @ ChrisC - Absolutely, but whilst I have the hub nuts off I want to make sure that its only the discs that need doing. Link to comment Share on other sites More sharing options...
DonDP Posted April 13, 2019 Author Share Posted April 13, 2019 I had a chance to use the dial gauge today.The rotor has a runout of 0.03mm.The drive flange has a runout of 0.018mm.The high and low spots are at the same places on the flange and rotor.On the other 'straight' side, the runout of both flange and rotor is under 0.003mm so something is definitely up.The questions I have are; is this just likely to be the rotor? if the rotor was deformed would that deform the flange? or is this likely an issue with something else, perhaps wheel bearing,bearing housing and/or driveshaft?opinions on best course of action welcome! Link to comment Share on other sites More sharing options...
SM25T Posted April 13, 2019 Share Posted April 13, 2019 Tiny spot of something between disc and hub ? Link to comment Share on other sites More sharing options...
Jim 123 Posted April 13, 2019 Share Posted April 13, 2019 Not sure if I know where I am going with this, but is the run out towards or away from the center line of the car, and over what percentage of the rotor and flange circumference do you get the run out? Link to comment Share on other sites More sharing options...
DonDP Posted April 13, 2019 Author Share Posted April 13, 2019 @ SM25T The hub flange and disk are both distorted (high and low) at the same points so I can’t see this being something between them. I take that to be that they are either both distorted, the disc is causing all the distortion, the wheel bearing/bearing assembly or driveshaft.@Jim123 not sure about which line compared to the car... however the the runout runs across whole rotor, hard to tell where the ‘straight’ part is... Link to comment Share on other sites More sharing options...
Tom_Arundel Posted April 13, 2019 Share Posted April 13, 2019 I think you have the decimal point in the wrong place in your readings otherwise they are insignificant Link to comment Share on other sites More sharing options...
ScottR400D Posted April 13, 2019 Share Posted April 13, 2019 I think you’re right and even so, it’s hard to see it causing a significant vibration except under braking. Link to comment Share on other sites More sharing options...
Jim 123 Posted April 13, 2019 Share Posted April 13, 2019 Sorry maybe this can clarify my question...... If you look at the disc by standing at the side of the car, like looking at a clock face, what proportion of the "clock face" i.e. the disc is distorted and is the distortion towards the inside of the car or is it a bulge out? Link to comment Share on other sites More sharing options...
DonDP Posted April 13, 2019 Author Share Posted April 13, 2019 @Tom_Arundel & @ScottR400D you are correct, my mistake, one too many zeros. Readings are 0.3mm (rotor) and 0.18mm (hub flange). Significant enough to visibly move the caliper at idle in 4th gear. This would be amplified significantly at the radius the tyre meets the road. It is 10x more runout that the other side. Something is definitely wrong. @Jim123 not sure, its difficult to work out where straight is!Might as well do new disk and wheel bearings and see what the measurement is. Worse case it will need need a drive shaft, hub flange and bearing carrier too... Link to comment Share on other sites More sharing options...
alcal Posted April 14, 2019 Share Posted April 14, 2019 Just a thought..I had a similar problem a few years ago which was resolved by having the wheels and tyres balanced by first mounting them on a tool used for balancing Citroen and Peugeot wheels which have no central hole. It seems that the centre holes on the Caterham wheels didn't correspond exactly to the centre point generated by the four mounting bolts. Link to comment Share on other sites More sharing options...
ScottR400D Posted April 14, 2019 Share Posted April 14, 2019 Still doesn’t seem too significant to me but you might as well change the discs. The caliper moves, you say? It doesn’t look like it in the video. I would just expect the pads to be pushed back the once and then stay there until the next braking. Didn't you also say you can’t feel this under braking? I would certainly expect it to be felt that way first. Re Alcal’s post, hardly anyone uses flange kits anymore except for close centre wheels. Most wheels can be balanced quite well with one cone or another. I have two sets of Apollos both of which have been balanced by me a couple of times and I’ve not had a problem just using a basic back cone. Link to comment Share on other sites More sharing options...
Tom_Arundel Posted April 14, 2019 Share Posted April 14, 2019 On a scale of 1-10, 1 being a slight irritation and 10 being about to crash, how bad is the vibration?Are you sure that it is at the rear of the car?Prop shaft runs in a plain bearing sleeve in the rear of the gearbox extension, bearing can wear and can be replaced ( with some difficulty)Does the gear lever vibrate? Link to comment Share on other sites More sharing options...
DonDP Posted April 15, 2019 Author Share Posted April 15, 2019 Thanks guys,I took a few videos of the caliper movement. You can see it quite well in , particularly if you look at the caliper slide pin boots.I haven’t felt it under braking but my thought are that this may be either because the entire axle path is off axis or as it is a single pot floating caliper on the rear the sliders may be masking it. Perhaps I should measure the wheel runout?I would say the vibration is a 5 out of 10. The vibration does not cause the vehicle to be unsafe at high speed, It just buzzes through you to a point you feel your head vibrating! there is no vibration at the steering wheel. Gearbox was rebuilt 1500 miles ago by road and race which is why I am hoping this is elsewhere on the car but good idea to see if the gear lever is vibrating on my next test run. Link to comment Share on other sites More sharing options...
Jim 123 Posted April 15, 2019 Share Posted April 15, 2019 It may be relevant to learn how come the rear axle, propshaft, and gearbox have been treated to rebuilds in the last 1500 or so miles on a 2014 car. Link to comment Share on other sites More sharing options...
DonDP Posted April 16, 2019 Author Share Posted April 16, 2019 @Jim123 The reason behind the rebuilds is that its an ex grad car, the previous owner bought it and then sent it to PT Sports Cars to get it to 310R spec. PT reportedly take the engine out for this work, so whilst engine was out it was a good opportunity to refresh the box. This also included the Titan diff upgrade which is why that is low on my list too.I took it upon myself to change the prop as I thought this might be the issue, unfortunately not...Thinking about it more. Before I order any parts, I am going to swap the disc/hub flange assemblies from left to right and see if this also moves the runout I am observing. Can start to rule parts out then. Link to comment Share on other sites More sharing options...
elie boone Posted April 16, 2019 Share Posted April 16, 2019 Why go trough all that trouble, just check them on a lathe, can't it be that the hub was not clean when the disc was mounted and this will give the run out ? Link to comment Share on other sites More sharing options...
DonDP Posted April 16, 2019 Author Share Posted April 16, 2019 @elie boone, great idea, need to find a local with a lathe! The run out is on the hub and the disc. Highest and lowest spots are in identical locations which is why I am not sure its an issue with how they are mounted together, but will definitely check that. Link to comment Share on other sites More sharing options...
Jim 123 Posted April 16, 2019 Share Posted April 16, 2019 As a precaution you may want to vernier check the thickness of your disc as you will probably end up removing the same amount off each side with the lathe. Best not to go below minimum thickness esp if you are tack daying. Link to comment Share on other sites More sharing options...
Tom_Arundel Posted April 16, 2019 Share Posted April 16, 2019 There should be a centre hole in the end of shaft that should run true if you can get your dial gauge into it. If its an ex Grads car it may have had an impact on the rear wheel at some time and bent the stub axle a bit Link to comment Share on other sites More sharing options...
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