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Old 23rd June 2021, 17:26   #1
xsport
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Default pinchbolts

the lower arm pinchbolts RYG101220 according to rimmers photo are not the new type with the thinner shank. i have received 2 new ones today from them with the thinner shanks. i have also ordered from mat at DMGRS a pair which have the thicker shanks and longer thread length so i might get a locknut on these. im a little unsure about using these thinner shank bolts as i have had nothing but trouble with them loosening and having to retighten them. you cant use a lock nut as well using the rimmer bolts ... too short for that. im going to torque them up higher. i would imagine that these thinner shanks are ok to use on new swivel hubs but if they do slacken off it wouldnt take much to elongate them on old hubs pinch holes. i had a knocking for a while on my car over the bumps but intended to renew roll bar bushes first. im going to replace both swivel hubs and use new pinchbolts but dont know which are best to use. the thicker shanks i have heard are more likely to rust in the hole but at least they stay put.the lower arms we get these days are not in long enough to worry about that !! do you think the bolts stretch or is it over torque that does it ? . sadly the old song comes to mind "things aint what they used to be".

Last edited by xsport; 23rd June 2021 at 17:31..
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Old 23rd June 2021, 18:24   #2
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Why not use Thread--Lock ??
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Old 23rd June 2021, 18:41   #3
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the nuts are pinched anyway but i dont suppose it would do any harm.
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Old 23rd June 2021, 18:56   #4
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I don't have the part numbers to hand but I ordered the bolts and nuts from Rimmers. The nut is a locknut of sorts. If you look at the side of the nut that the bolt will end up poking its head through, you'll notice it's not perfectly circular. It has almost an oval shape.

Learnt all this as when I received them I thought they were the wrong nuts as they wouldn't thread on by hand after a point. So I phoned Rimmers and they took me to school!
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Old 23rd June 2021, 19:41   #5
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Quote:
Originally Posted by xsport View Post
the lower arm pinchbolts RYG101220 according to rimmers photo are not the new type with the thinner shank. i have received 2 new ones today from them with the thinner shanks. i have also ordered from mat at DMGRS a pair which have the thicker shanks and longer thread length so i might get a locknut on these. im a little unsure about using these thinner shank bolts as i have had nothing but trouble with them loosening and having to retighten them. you cant use a lock nut as well using the rimmer bolts ... too short for that. im going to torque them up higher. i would imagine that these thinner shanks are ok to use on new swivel hubs but if they do slacken off it wouldnt take much to elongate them on old hubs pinch holes. i had a knocking for a while on my car over the bumps but intended to renew roll bar bushes first. im going to replace both swivel hubs and use new pinchbolts but dont know which are best to use. the thicker shanks i have heard are more likely to rust in the hole but at least they stay put.the lower arms we get these days are not in long enough to worry about that !! do you think the bolts stretch or is it over torque that does it ? . sadly the old song comes to mind "things aint what they used to be".
If Your having to retighten your pinch bolts are you overtightening and stretching them ? as once tightened should not become loose. A bolt should be tightened within the designed yield strength which is determined by the tensile strength . Torque setting are not just for tightening bolts but are also to prevent over tightening of bolts past the yield point rendering them deformed ( ie stretched ) If you have to retighten any bolt after tightening I would always renew the bolt as a precaution

I would certainly recommend changing out the two pinch nuts and bolts sooner rather than later !

Either the Rimmers nut and bolt or DMGR's nut and bolt with the correct tensile strength should not need any other locking nut to keep them secure once tightened correctly

Once tightened if your hub is still loose on the lower arm ball pin the fault lies with either hub or lower arm. Wear as you say in the hub or indeed the pin can cause this
When fitting the pinch bolt coat the shank with copper grease or similar to aid removal at a later date

Last edited by TourerSteve; 23rd June 2021 at 20:15..
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Old 23rd June 2021, 22:07   #6
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i think the problem lies with the swivel hub pinch holes . not really elongated but certainly worn after 20 years. i am fitting new swivel hubs arms and pinchbolts as mentioned in my post but didnt want to use the thinner shank ones. im going to try mats version as the shanks are thicker. i think they fit tighter to the pin recess on the arms. copper grease i always use and have not had problems removing with the old thicker style bolts. does it make any difference to which side of the hub that the nut is mounted on the through bolt..... ? i usually put mine on to face the rear of the car unless they should be the other way round ... ? thanks for replies.

Last edited by xsport; 23rd June 2021 at 22:22..
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Old 23rd June 2021, 22:20   #7
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just to come back to the last post .the hubs are not loose after tightening.they seem to work loose after 6 to 9 mths and show up again at mot time. this is using the thin shank bolts. had 6 new arms on the car to date and never had a problem even when i re used the old thicker bolts.it just seems more than a coincidence it started with these bolts or maybe the swivel hubs are ready for change. pin sizes on the trw arms are correct diameter and tighten up fine..... for a while. members on here have recommended 60 to 70 torque figures and claimed to have cured this problem as apparently its a common occurance. but i must admit i stuck to around 50. we will see what happens after the new stuff has gone on..... thanks for replies.
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Old 24th June 2021, 06:55   #8
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Quote:
Originally Posted by xsport View Post
just to come back to the last post .the hubs are not loose after tightening.they seem to work loose after 6 to 9 mths and show up again at mot time. this is using the thin shank bolts. had 6 new arms on the car to date and never had a problem even when i re used the old thicker bolts.it just seems more than a coincidence it started with these bolts or maybe the swivel hubs are ready for change. pin sizes on the trw arms are correct diameter and tighten up fine..... for a while. members on here have recommended 60 to 70 torque figures and claimed to have cured this problem as apparently its a common occurance. but i must admit i stuck to around 50. we will see what happens after the new stuff has gone on..... thanks for replies.
Over torqueing providing your still within the bolt yield strength will not be a problem but once taken beyond that point a bolt will not recover . Hence good practice to fit new bolts on bolts that have come loose
Torque figures given are to get the bolt into its yield strength with adequate tightness, but not beyond , rendering the bolt reusable without deformation .
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Old 25th June 2021, 13:53   #9
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received my pinchbolts from mat at dmgrs today and they look substantially thicker on the shank. much beefier than the rimmers ones. the bolt heads are flanged the same and are about one mm larger diameter. good ! the shanks are near on 2mm thicker ... good ! the extra thickness shank will now result in less up/down play if for some reason they do work loose especially on a worn hub. the nuts are not as good as rimmers in my opinion as they are slightly chamfered on the outer edge so about 1mm purchase depth lost in the socket . the only downside i can see is that they are "black finish " shanks but im a novice and have zero knowledge of bolts manufacture expertise. would corrosion be more of a likely event with the black finished shanks (both nuts and bolts are correctly stamped grades ) given that they are back to original size rimmers used to use ? with a liberal dose of copper grease before fitting should the "black finish shanks " present a more likely rust welded bolt seizure in the hub. im not sure given that the original rover bolts did... hence the shank size reduction. or does it come down to no copper grease upon assembly. ...
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Old 25th June 2021, 15:38   #10
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The black oxide finish actually helps prevent corrosion attacking the bolt, they will still suffer corrosion over time, a good coat of copaslip will help.
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