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Peter Scully
United Kingdom
161 Posts |
 Posted - 04/08/2010 : 22:43:10
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| I'm intending fitting 4.50x19 Blockley tyres and note that although they will fit 2 1/2 inch rims the optimum is 2 3/4. I will be fitting the tyres to new wheels and so was wondering whether it was worthwhile getting 2 3/4 or 3 inch rims? Any advice gratfully received. |
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Terry Andrews
United Kingdom
546 Posts |
Posted - 05/08/2010 : 10:19:34
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Hi Peter,
I have investigated this for some time now as I need to decide rim width for my N type. Richard Bros do a large range of rims widths. I know many people who have used them including me. When John Day had the N 4 seater we had a great debate on this. The issue is that if you fit a tyre on a narrow rim the centre is pushed to a peak so that not all of the tread is in contact with the road as the tyre manufacture had intended. This makes the car a little “Skittish”. By going wider or to the recommended width of the tyre manufacture then the car is more stable on the road. This was confirmed to me by Richard Bros. This is particularly important if you use a make of tyre which has a stiff carcass, i.e. not as supple as Blockly tyres. Blockly also agreed but said that their tyres ( at a pinch, excuse the pun) could be used on 2 ˝ inch rims. I have mentioned this to several N type owners and Keith Portsmore (not using Blockly’s) had some wider rims made like John day and reported to me that the car was much better on the road.
I am awaiting the first fit of my N body as there is a clearance issue with the rear wings but I think I will be going for 3 inch on the N.
Am I correct in thinking you have a P type? If so I would not use 4.50 x 19 but 4.00 x 19. I used 4.50 x 19 when the smaller size was not available, like we all did years and years ago. However, when I had the opportunity to change to 4.00 x 19 the car was better the steering was lighter and the milometer was then spot on.  Wider rims with 4.50 x 19 tyres may make a little P or J type look a little heavy? See also the internet on Blockly's going out of shape if the cars is left standing for a few weeks.
It is your car so you decide…… regards…. Terry
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Peter Scully
United Kingdom
161 Posts |
Posted - 05/08/2010 : 10:45:16
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Hi Terry
Your point about the effect of the narrow rim on the tyre tread shape was what was worrying me, hence the consideration of the wider rim. Yes I do have a P-type and currently have 4.00x19 tyres on standard rims but feel that, with cycle wings, the car looks a little 'under-tyred'. Although I also take your point that fitting the bigger tyres may make it look a little heavy!
Oh, decisions, decisions.
Regards,
Peter |
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etlanpa
United Kingdom
560 Posts |
Posted - 05/08/2010 : 11:02:35
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On all the cars where I've replaced road tyres with Blockleys (like for like in size), they've always looked less under-tyred (if you get my drift!). The tread width on Blockleys is only marginally less than the overall carcass width, whereas on some tyres (eg. Dunlop Goldseal) the tread width is noticeably narrower than the overall width....
I'd go with Terry on this one! |
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George Eagle
United Kingdom
3244 Posts |
Posted - 06/08/2010 : 12:16:31
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Hi Peter
I faced this problem with my blown NB. Blockley had just produced their new 4.50/5.00 x 18 tyre. My car is fitted with 3 1/4 inch 60 spoke rims which I thought would be too wide for the new tyres.
I wanted to replace the slightly over sized Avons and contacted Blockleys who advised me the tyres would be perfectly ok on my rims. They have improved the road holding and certainly look very good on the NB - no bulging sides and the car does not look under tyred.
I decided to fit 60 spoke rims as several N type owners, including the late Bob Brassington, advised me they had experienced problems with broken spokes.
Regards George
NA0960 |
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Bob Grunau
Canada
290 Posts |
Posted - 30/10/2010 : 14:37:51
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| I am considering new wheels for KN0389 4 door pillarless saloon. The car is quite heavy at approx 2352 pounds ( 21 cwt ) + passengers, tools etc and I think the original 48 spoke 2 1/2" x 19" outer laced wheels may be marginal. I intend to fit Blockley tyres, probably 5:00 a 19" (originals were 4.75/5.00 x 19"). I am considering 3" x 19" - 60 spoke wheels to suit the tyres. Any comments on suitability of tyres and wheels and source of supply appreciated. best regards from Canada, Bob Grunau |
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Bob Stringfield
United Kingdom
854 Posts |
Posted - 30/10/2010 : 15:37:42
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My experience with changing the PA from 4.50 to 4.00 x 19 Excelsior tyres exactly agrees with that of Terry Andrews. The looks were improved, IMHO.
Vintage Austin Sevens, with their 12 bhp, do suffer from broken spokes, often on the n/s rear. I feel that neither power nor weight is responsible. |
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John Reid
United Kingdom
705 Posts |
Posted - 31/10/2010 : 23:04:27
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Help please! I have always found it very hard to get accurate dimensions/specifications for wheels. Does anyone know what the various rim offsets should be for the different widths of wheels being discussed? I would have thought that you need to know this in order to maintain clearance between tyre and body work.
What do you specify on the order to the wheel supplier?
Or is it just a question of adding the extra width to the outside of a standard rim so that tyre to body clearance is maintained? So for example, if you go from 2.5" to 3" then the outside rim is 1/2" further out and the inside rim stays in the same place wrt the hub?
John R |
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Rodney Collins
United Kingdom
424 Posts |
Posted - 01/11/2010 : 12:41:49
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Hi All
I bought new 4.50x19 blockleys for my PA when I resored it, i had no problems what so ever the car felt solid on the road turned in well, and I never found any distortion if the car was left standing.Perhaps I was lucky!
Rodney |
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tonym
United Kingdom
655 Posts |
Posted - 01/11/2010 : 16:12:35
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Wheel offsets
Who knows what is actually correct?
It is no good just going out and measuring yours and assume that that is what is right. Remember your wheels [unless they are brand new] have been probably rebuilt several times in the nearly 80 years that our cars have been around.
I would very much like to see some period documentary evidence as to wheel offset. Anybody got this info?? I have never found any - despite a search at the British Library
Moving a rim out [or in] in relation to the wheel centre is limited to about ˝" - mainly by the size of the hole in the dimple restricting movement of the nipple
Tony |
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rodb
New Zealand
260 Posts |
Posted - 01/11/2010 : 20:28:05
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It is my understanding the wheel offset ( terms used in the wheel trade are inset, outset, and back spacing)is determined by taking a line through the king pin centre line and extending it down to the ground at static ride height. At this ground position the wheel offset is distributed to prevent tyre scuff.
A J2 2.5” x 19” wheel has an 8.8mm outset (measured from the wheel centre line to the back face of the wheel centre) and a 39mm back space (measured from the same hub back face to the inner edge of the rim). These measurements are only accuratley determined from engineering drawings. I assume the P type wheel is the same.
I would contact Motor Wheel Services to get expert advice on how to distribute the extra rim width across the outset and inset.
There is a works drawing (J4)that copies exist of, that I was kindly given by someone (do not remember who) who supplied me with a J4 divided steering system some years ago. From this drawing you can determine the position of the hub relative to the rim and the king pin centre line.
Rod B NZ
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