steyning Posted August 8, 2008 Share Posted August 8, 2008 I know I may sound very stupid to some but ....is a swap to the 16" HPC wheels a straight swap with 13 or 14" Minilite type wheels currently fitted on a Caterham? Does the speedo require recalibrating or does the tyre size on the bigger HPC wheels compensate? What about the bodywork - are the cycle wings a special size too to allow for the wheel diameter. Any simple advice much appreciated 😬 Link to comment Share on other sites More sharing options...
Dickie Normuss Posted August 8, 2008 Share Posted August 8, 2008 It's likely that you'll have to change the front cycle wings as there are two sizes, one for 13/14" wheels and one for 15/16" wheels. Not sure how it will affect the speedo as the overall circumference will be similar as they use a lower profile tyre, some speedo's have 'dip switches' on the back that can be adjusted to give a more accurate reading. Generally people move away from the HPC wheels to get better handling. VX HPC - Loud and proud here Watch out, whatever hits the fan will not be distributed evenly Link to comment Share on other sites More sharing options...
andy_h Posted August 8, 2008 Share Posted August 8, 2008 Agree with the wing comment above - If you have lots of space between current wings and top of tyre (when looking from the side) then you may be ok. If not then you'll have to change the wings stays and possibly the wings as they're longer. Original build dash speedos (cable type) are connected to the gearbox. From looking underneath the 7 follow the cable and it should enter the Near Side of the gearbox. So wheel dims shouldn't matter. If you have a bike computer type then you'll need to re-set the calculation within the computer. Cheers, Andy White road legal 2.0 HPC VX race car 😬 Link to comment Share on other sites More sharing options...
millsn Posted August 9, 2008 Share Posted August 9, 2008 why? ride gets worse, handling gets worse Link to comment Share on other sites More sharing options...
neil.cavanagh Posted August 9, 2008 Share Posted August 9, 2008 I never noticed the ride being significantly worse on mine with 16" wheels. The speedo reading WILL be different. As mentioned the speedo drive is taken from the gearbox output, which will be unchanged. However the 16" wheels & Tyre combo has a larger circumference, so you will be going further for ever rotation of the wheel, so the speedo will say you are going slower than you were before. Or rather for the same speedo reading you will be travelling faster. In my car this means the speedo is more accurate: 16" wheels speedo 80 mph = c. 73mph true. 13" wheels speedo 80 mph = c. 68 true This is the 1st advantage of the 16" wheels... if you are going on a long distance drive with lots of constant speed cruising you will effectivly have longer gearing making it more relaxed. This is then a downside if you are on a twisty track or road.. The ride height will also be a good inch or so higher (if you leave suspension as is) which is useful on bumpy roads. And probably saved my sump when I bounced up a 12" high curb in the US in '05. Link to comment Share on other sites More sharing options...
Mavic82 Posted August 9, 2008 Share Posted August 9, 2008 As already posted the only issue you may have is the front wing stays. As for the ride and handling. Yes there is a little loss of ride comfort but this will be more effected by spring rate. As for the loss of handling I would say I disagree. The ultimate limit of adhesion is slightly higher. What people useually refer to regarding loss of handling is actually the reduction in progression to the point where adhesion is lost. On 13" wheels you have very soft side walls so you get plenty of lateral movement and warning of a slide. With the 16's this is much less and the transition is quicker which does mean you need to be very aware. However I would argue this actually adds feel because the time taken for the transition from grip to slip is much reduced. BUT you do have to be quicker to catch the slide and perhaps in some eyes this reduces the 'fun'. Having said all that for track use I would probably use 14"or 15" and 16" for the road, personally like the look too. I have done several track days on 16's and had a great time Link to comment Share on other sites More sharing options...
Dartmoor7 Posted August 9, 2008 Share Posted August 9, 2008 Regarding ride height and speedo accuracy, people continually talk about wheel size changing them, but it's the tyre size that counts. If you currently have 185/70x13, the 205/45x16 leaves ride height and gearing unchanged. If you currently have 185/60x13, the 205/45x16 gives 19mm increase in ride height and actual road speed is 6.8% greater than speedo (*IF* speedo set for 185/60x13 which was not usually an OEM size). If you currently have 185/60x14, the 205/45x16 gives 6 mm ride height increase and the road speed is 2% greater than speedo. If you have 195/50x15, the 205 gives a 6mm increase in height and road speed is 2.3% faster. OR YOU COULD FIT 16" WHEELS AND GO LOWER. 205/40X16 are available, which would give a 10mm drop from 185/70x13! MY BLAT-O-METER 2008: 49 (to 8th August) 2007: 70 2006: 89 2005: 91 2004: 64 2003: 66 2002: 66 2001: 79 2000: 32 (divorce!) 1999: NRA Edited by - Custer Cat on 9 Aug 2008 16:40:40 Link to comment Share on other sites More sharing options...
neil.cavanagh Posted August 9, 2008 Share Posted August 9, 2008 CusterCat. I think your maths has gone wrong somewhere. A 205/45 tyre has a sidewall of 102.5 mm (50% of 205 width). Add this to the wheel radius (half of 16") and you have a total height from wheel centre to ground of 295.45 mm. Compared to others this is the highest: WIDTH aspect tyre Wheel Height 205 45 92.25 16 295.45 185 70 129.5 13 294.6 195 50 97.5 15 288 185 60 111 13 276.1 Link to comment Share on other sites More sharing options...
Dartmoor7 Posted August 9, 2008 Share Posted August 9, 2008 Afraid not Neil. 205/45x16 has a sidewall height of 92mm. 45% of 205. The clue is in the 205/45x16. Link to comment Share on other sites More sharing options...
Dickie Normuss Posted August 9, 2008 Share Posted August 9, 2008 I was sure my sidewalls were nowhere near 92mm so I've just been an checked. From the wheel rim to the tyre face is 72mm. I assume the 95mm includes the portion of the sidewall inside the wheel? VX HPC - Loud and proud here Watch out, whatever hits the fan will not be distributed evenly Link to comment Share on other sites More sharing options...
Dartmoor7 Posted August 9, 2008 Share Posted August 9, 2008 Yes. Also, remember these figures are nominal, and will vary slightly between manufacturers. Edited by - Custer Cat on 9 Aug 2008 15:56:40 Link to comment Share on other sites More sharing options...
Dickie Normuss Posted August 9, 2008 Share Posted August 9, 2008 20mm isn't slightly ❗ VX HPC - Loud and proud here Watch out, whatever hits the fan will not be distributed evenly Link to comment Share on other sites More sharing options...
Dartmoor7 Posted August 9, 2008 Share Posted August 9, 2008 Ric, I'm not saying the hidden bit varies slightly, my answer was 'yes' to your question and then I added the extra comment. All tyres vary slightly between brands, one maker's 205/45x16 will not have identical measurements to another's. Link to comment Share on other sites More sharing options...
k.russell Posted August 9, 2008 Share Posted August 9, 2008 My original 16 wheel stay on my 92 HPC also had the tube reduced to half its width to clear the tyre wall on both the front and rear stay. it came with HPC wheels and 16" Goodyear eagles, i sold them around 15 years ago, so cant really comment on the difference in the handling Kevin R black(but sometimes orange)-ali HPC here Link to comment Share on other sites More sharing options...
Dartmoor7 Posted August 9, 2008 Share Posted August 9, 2008 I've had both wheel sizes and largely agree with Mavic, especially regarding how fast you have to be to catch the 16s when they go. I also noticed a great difference in tyre grip between winter and summer. Link to comment Share on other sites More sharing options...
neil.cavanagh Posted August 9, 2008 Share Posted August 9, 2008 um... custer.. I think you are forgetting that whilst the tyre wall height of a 205/45 is lower than a 195/50 they are running on a rim that is an inch bigger..... I have run 195/50 R15s and 205/45 R16s on my car and the actual fact matches up to the figues. 16" wheel combo is significantly taller. Link to comment Share on other sites More sharing options...
henry21p Posted August 9, 2008 Share Posted August 9, 2008 just phone george polley - the man there gave me the diameters of each of the tyre choices in each size and lots of advice. Link to comment Share on other sites More sharing options...
Dartmoor7 Posted August 9, 2008 Share Posted August 9, 2008 "I have run 195/50 R15s and 205/45 R16s on my car and the actual fact matches up to the figues. 16" wheel combo is significantly taller." I make it a 6mm ride height increase (admittedly based purely on the maths as opposed to real-life tyres).That's only the difference between a new tyre and one on the wear bars. Link to comment Share on other sites More sharing options...
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