17-05-2021, 09:52 AM
Jake,
Assuming that you have bought the three bearing Ruby you mentioned earlier, it should be running on 4.00 (or 4,50) X 17 rims and tyres. 4.00 X 17 tyres rotate at approx 800 revs per mile, giving 14.29 mph per 1000 engine revs is top and 4.50 X 17s at 785 revs per mile, giving 14.56 mph per 1000 rpm.
3.50 X 19 rims and tyres rotate at 775 revs per mile, giving 14.75mph per 1000 rpm.
So, not much variation. Assuming the standard 5.25:1 diff, 45mph represents about 3000 rpm in top.
Austin Seven engines always sound busy: my RP (on 5.25:1 diff and 3.50 X 19 rims) is just this at 40 -45 mph, but has covered a lot of miles running at this sort of speed. A well sorted engine is really quite robust.
Hope this helps and gives some perspective on engine speed.
Assuming that you have bought the three bearing Ruby you mentioned earlier, it should be running on 4.00 (or 4,50) X 17 rims and tyres. 4.00 X 17 tyres rotate at approx 800 revs per mile, giving 14.29 mph per 1000 engine revs is top and 4.50 X 17s at 785 revs per mile, giving 14.56 mph per 1000 rpm.
3.50 X 19 rims and tyres rotate at 775 revs per mile, giving 14.75mph per 1000 rpm.
So, not much variation. Assuming the standard 5.25:1 diff, 45mph represents about 3000 rpm in top.
Austin Seven engines always sound busy: my RP (on 5.25:1 diff and 3.50 X 19 rims) is just this at 40 -45 mph, but has covered a lot of miles running at this sort of speed. A well sorted engine is really quite robust.
Hope this helps and gives some perspective on engine speed.