John h Posted February 23, 2019 Report Share Posted February 23, 2019 Hi all been reading a lot about the trailing arm studs/helicoils unf vs unc A lot of the posts were from seven or eight years ago what is the best solution i’m thinking UNC and using Loctite to hold them in am I on the right track or should I just go with 5/16 UNF and use existing studs I’ve even had one suggestion to leave them alone basically if it’s not broke don’t fix it is it a mod that should be done many thanks John Quote Link to post Share on other sites
RogerH Posted February 23, 2019 Report Share Posted February 23, 2019 Hi John, indeed 'if it ain't broke don;t fix it' is true. You could give the studs a test by applying the max torque figure PLUS 10%. If they feel OK keep them. If they need changing then give a thought to the size of stud. 3/8 UNC sounds much better but consider that the original, 5/16unf, have lasted 50 years. The 3/8 UNC do not need helicoils - but you remain with stud in Ali configuration. I would not use Loctite. 5/16 UNF + helicoil gives a very strong bond - the helicoil giving a serious sideways grip - thus less tendency to strip the threads etc. IF you do replace the studs you WILL need an alignment jig to keep the holes perfectly square etc. I can help there. roger Quote Link to post Share on other sites
John h Posted February 23, 2019 Author Report Share Posted February 23, 2019 Thanks roger the length of the helicoil is it 1.5 d and thanks for the offer of a jig i managed to pick one up a little while ago many thanks John Quote Link to post Share on other sites
Steves_TR6 Posted February 23, 2019 Report Share Posted February 23, 2019 I went for the kit from CDD inc hiring of jigs, worked well for me. steve Quote Link to post Share on other sites
John h Posted February 23, 2019 Author Report Share Posted February 23, 2019 Hi all I’ve just done the test suggested by Roger starts starting to strip so it’s gonna have to be helicoils many thanks for reply’s will let you know how I get on . John Quote Link to post Share on other sites
ChrisR-4A Posted February 23, 2019 Report Share Posted February 23, 2019 +1 for the CDD shouldered studs, 3/8 unc x 5/16 unf only thing is the new threads need to be deep enough so that none of the 3/8 shoulder is proud of the hole but also not too deep otherwise the stud will turn when fitting the nyloc nut. I used a dab of studlock and left overnight before final assembly. Roger, can you expand on your comment on locktite. Chris Quote Link to post Share on other sites
RogerH Posted February 23, 2019 Report Share Posted February 23, 2019 Hi Chris, Triumph went for UNF on the stud in the Ali to stop the tendency of the stud vibrating free. These have last a very long time. Loctite should not be required simply because it never was required. The 3/8 UNC does not give you the vibration security that the UNF does. Why reinvent the wheel. I feel the CDD studs are wrong. Roger Quote Link to post Share on other sites
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.