Bob Horner Posted February 12, 2020 Report Share Posted February 12, 2020 I've just got some 13" repro Dunlop D1 type wheels they are 5.5 rims for my Mk2 GT6. Seems that recommended tyre size is 175 70 R13s but personally prefer something a bit narrower. I know 155 80 would have been original fitment but these would be a bit thin for 5.5" rims? Would there be any issues with fitting 165 80 tyres (apart from choice). I know there may be issues with the speedo but then I believe the car had a 3.27 diff but has now got an overdrive and a 3.89 diff. Any thoughts on the above gratefully received. Bob Link to comment Share on other sites More sharing options...
johny Posted February 13, 2020 Report Share Posted February 13, 2020 I like 165 80 13 on my Vitesse as I think they look good and are bigger diameter than the 175 you mention which would help a bit to correct your speedo error. This site is very good for checking different combinations of tyres and diffs (the OD itself doesnt make any difference to speedo reading): https://richyrichracing.com/tools/gear-ratio-speed-calculator-for-standard-triumph-drivelines/ The only downside is that this size is getting harder to find and the choice is pretty limited.... Link to comment Share on other sites More sharing options...
Nigel Clark Posted February 13, 2020 Report Share Posted February 13, 2020 175/70-13 is the ideal size for a 5.5" rim and keeps the same rolling radius as original. Take care with 165/80-13, they may fit okay but could be close to the rear arches. How about 165/70-13? Slightly reduces rolling radius but probably not enough to matter. Nigel Link to comment Share on other sites More sharing options...
Peter Truman Posted February 13, 2020 Report Share Posted February 13, 2020 I run 165 by 75 by 13in Michelin’s on both the Mk2 Spit & Vitesse my son who works for M advised they were nearest the original Crossplys. Both cars have 5in wide wheels The Vitesse tyres are now old 10 years and he’s trying to get me replacements getting difficult to get Quality tyres for 13 inch wheels. I’ll advise when he tells me he’s found good end, I can wait as he gets them at the ultimate discount. Peter T Link to comment Share on other sites More sharing options...
Bob Horner Posted February 13, 2020 Author Report Share Posted February 13, 2020 The issue of 165 80 and rear arch clearance is one of the reasons I'm slightly nervous of that size. It currently has 175 70 13 on slot alloys (which I'm not a fan of) and there seems to be too much space in the arches for my liking at the moment. The problem is that the car is a non runner so its hard to judge until its on the road and the suspension has settled (which I hope will be within the month). The car has been off the road for more than 10 years so the rubber that's on it is knackered and don't have the option of driving it for a while on the old tyres. Bob Link to comment Share on other sites More sharing options...
johny Posted February 13, 2020 Report Share Posted February 13, 2020 Id be surprised if the 165 80s give you an arch clearance problem (assuming you have wheels with the correct offset of course) as its normally width that does that. The biggest risk on increasing diameter is contact with the bulkhead on sharp turns and even there I dont think the <10mm increase will be an issue in this case... Link to comment Share on other sites More sharing options...
Ian Foster Posted February 14, 2020 Report Share Posted February 14, 2020 Bob Unless you are absolutely sure that the offset is correct, you might want to do a trial fit of the wheels before committing to tyres. 5.5" Dunlops I had on my GT6 Mk2 2 when I bought it in 1977, did have quite a lot of projection from the arch and sprayed the side of the car. (don't know the offset). They were sold (probably too cheap) when I put on some 5.5" Cobra Superslots. I'm now running repro 5.5" Revolutions (ET=+25mm), spaced 5mm at the front for top wishbone clearance and 5mm at the rear to fill the arches a little better. It's a a bit of a minefield. Ian Link to comment Share on other sites More sharing options...
Colin Lindsay Posted February 14, 2020 Report Share Posted February 14, 2020 My Mk3 GT6 had period alloy wheels and when I bought my Mk1 I transferred them over. I saw huge cuts out of the rubber one day, it turned out that the inner lip of the wing where it bent into the wheelarch was cutting into the tyres. Every time I went over a bump they made contact not with the top but the side. The later car had a much thinner return lip and it didn't affect the tyres at all, but on the Mk1 it was like a knife edge, and I immediately went back to narrower original wheels before we had a disaster. It's something worth checking if you fit wider wheels. Link to comment Share on other sites More sharing options...
Nick Jones Posted February 14, 2020 Report Share Posted February 14, 2020 On 13/02/2020 at 17:27, johny said: Id be surprised if the 165 80s give you an arch clearance problem (assuming you have wheels with the correct offset of course) as its normally width that does that. The biggest risk on increasing diameter is contact with the bulkhead on sharp turns and even there I dont think the <10mm increase will be an issue in this case... Exactly this. But wheel offset/ET is also an important factor. Do you have an ET figure for the wheels? Nick Link to comment Share on other sites More sharing options...
Bob Horner Posted February 14, 2020 Author Report Share Posted February 14, 2020 Hi chaps. Thanks for the input so far. The offset is +16 . Bob Link to comment Share on other sites More sharing options...
johny Posted February 14, 2020 Report Share Posted February 14, 2020 Surely the wheels you bought must be the right offset or did you just buy on chance? If you bought correctly for 175/70 sure 165/80 wont give you any problems..... Link to comment Share on other sites More sharing options...
Nick Jones Posted February 14, 2020 Report Share Posted February 14, 2020 +16 sounds promising. + 25 is too much (even though some sellers are marketing wheels for small chassis Triumphs with ET25). Hence Ian’s need to add 5mm spacers giving him effectively ET20. With just 4mm more I reckon you are in the happy zone. I had problems with tyre rub on the bulkhead with 165/80 on 5.5”Dunlop steels on my Herald years ago. Not really comparable with your situation but has meant I’ve tended to stick with 175/70 on Vitesse, GT6 and Spitty with good results. The Falken SN832 is reasonably priced, excellent in the wet and seem to wear quite well too. Nick Link to comment Share on other sites More sharing options...
Sparky_Spit Posted February 15, 2020 Report Share Posted February 15, 2020 165/80s on 5.5" Minilite-alikes do rub slightly on my Mk3 Spitfire front bulkhead on quick tight turns, but only just. Careful dressing with a padded mallet solves the problem but might not be your choice if you want a perfect looking car. Link to comment Share on other sites More sharing options...
Peter Truman Posted February 15, 2020 Report Share Posted February 15, 2020 thought this might interest you on ebay 7in wide Magnesium wheels now these would definitely rub on the bulkhead,, and if you run flat would definitely create a BRIGHT fire! Peter T Link to comment Share on other sites More sharing options...
Dave the tram Posted February 23, 2020 Report Share Posted February 23, 2020 I had similar dilemma with my GT6 Mk 3 - 155 looked a bit thin and didn’t seem to have enough rubber on the road. Twitchy through bends in the wet. I went for Falcon Sincera 165 70 as they got good reviews (including on the forum) as a wet weather tyre and quite cheap (less than £40 each I think online then got my garage man to fit them). They look perfect and transformed the handling with no clearance issues. My speedo was low due to diff change to give slightly more relaxed cruising. I think 165 70 gave very slightly smaller diameter than 155 80, so will have dropped the gearing a fraction, but not so you’d notice. Cheers Dave Link to comment Share on other sites More sharing options...
Bob Horner Posted March 9, 2020 Author Report Share Posted March 9, 2020 Just an update on this. Went for Falken sincera 165 80 R13s on the Dunlop D1 replicas noted above, and, subject to road testing a bit more, all seems to fit with no issues. Regards Bob Link to comment Share on other sites More sharing options...
Guest Posted March 9, 2020 Report Share Posted March 9, 2020 On 14/02/2020 at 21:40, Nick Jones said: +16 sounds promising. Hello Nick, The off the shelf Dunlop D1's are indeed +16 offset - infact it is the only offset offered for that particular wheel on a 13" rim. Regards. Richard. Link to comment Share on other sites More sharing options...
Nick Jones Posted March 10, 2020 Report Share Posted March 10, 2020 My point (not well made) was that several of the new wheel types made available in period styles (Revolution 4 spoke for one) are only available in ET25 which is too much onset and actual catches on wishbones making the use of a 6mm spacer necessary. Nick Link to comment Share on other sites More sharing options...
SpitFire6 Posted March 10, 2020 Report Share Posted March 10, 2020 On 14/02/2020 at 21:40, Nick Jones said: +16 sounds promising. + 25 is too much (even though some sellers are marketing wheels for small chassis Triumphs with ET25). Hence Ian’s need to add 5mm spacers giving him effectively ET20. With just 4mm more I reckon you are in the happy zone. I had problems with tyre rub on the bulkhead with 165/80 on 5.5”Dunlop steels on my Herald years ago. Not really comparable with your situation but has meant I’ve tended to stick with 175/70 on Vitesse, GT6 and Spitty with good results. The Falken SN832 is reasonably priced, excellent in the wet and seem to wear quite well too. Nick 16 + 5 =ET11. Not ET21? Link to comment Share on other sites More sharing options...
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