Smaller wheels

[Adam H]

I was at CC the other week getting a couple of minor things looked at and casually asked whether it would be worth spending a few hundred quid on a replacement exhaust (probably 4-2-1) for my 1994 1400ss (currently with standard 4-1 inside engine bay). I was told that for the money, the performance increase wouldn't be massive and that I would really have to want/need a new exhaust to make it worthwhile.

 

After one look at my car every member of staff told me to change the wheels instead, to gain a better performance increase than changing the exhaust would give. The car is currently running on 16" HPC wheels with Avon ZZ3's. I was told to swap them for 13" wheels with CR500 tyres and that if I did so I would notice a big difference in both acceleration and handling.

 

What I didn't think to ask when I was there was whether the speedo needs re-calibrating if it has been set up using larger wheels and also whether the ride height will need adjusting.

 

Also, if I sell the HPC with tyres (only done 1000 miles) what should I ask for them?

 

Any ideas?

 

If these are stupid questions please excuse, novice is definately the word ❗

 

Adam

1400ss 6sp

 

Edited by - adam h on 10 Oct 2005 17:40:21

[Normans_Ghost]

Adam, don't apologise for asking questions on here. this is what TechTalk is for.

 

The performance will improve because you will be lowering the gearing, but you will some top speed. I suspect the handling bit may be up for discussion. The speedo should need recalibrating but as they're not that accurate in the first place don't worry about it. Get it checked against a GPS unit such as a road anget so you know just how far out it is.

 

The ride height will be lowered, in theory, by 1.5 inches. If you have adjustable platform then this is relatavley easy, not so if it's fixed. However depending on your current tyre sizes the drop may not be anywhere as much.

 

Norman Verona, 1989 BDR 220bhp, Reg: B16BDR, Mem No 2166, the full story here

[MusCat]

The exact difference in size will depend on the profile of your current 16" tyres and the profile of the 13" tyres you intend to use but by the sounds of thing you'll be ending up with much smaller diameter wheels/tyres. Just checked and CR500s are 175/55/13s which are low profile so you'll have very small wheels (about a small as you can get)

 

A few things to consider:

You are effectively lowering the gearing of the car so you'll get better acceleration but a lower top speed. You'll be running at higher revs when cruising at high speeds (any speed in fact), so you'll use more petrol (not something most Caterham owners worry about). If you do track work you might find it runs out of legs on the long straights.

 

Your ground clearance will decrease. Small decreases in wheel diameter can be lived with, with care being taken when getting used to it. But going from 16" to 13" will undoubtably require some readjustment to the ride height.

 

Your speedo will require adjustment.

 

Your wheels will no longer fill the wheel arches which can look odd to some.

 

IMHO it would appear a big move. No great expert on 1400s (I've got an xflow) but is there anything you can do to the engine?

 

Tim

 

 

 

[neil.cavanagh]

I run two sets of wheels on my SV:

 

16" with 205/45 tyres and 13" with 185/75 on them.

 

The 13" wheel/tyre combo does have a significantly smaller circumference. Probably 10-15%.

 

The ride height is a lot lower, to the extent that with the settings I have for the big wheels I drag my sump a lot when on the 13" wheels. BUt as I use the small wheels pretty much exclusively on the track this is not a problem.

 

The other big advantage from the smaller wheels is down to the weight saving. They weight a good 3kg+ or so less per corner I think. The difference is very noticable when swapping them over. This means the whole car just feels more alive when on the small wheels. The suspension reacts quicker, and car accelerates and brakes better and overall is far more lively.

 

I find having both sets of wheels works well, using the 16" for touring holidays, and the 13" for local blats and track work....

[Golf Juliet Tango]

You might like to have a read through some of these articles on the CC website

http://www.caterham.co.uk/aftersales/index.htm

Click through on Drivetrain upgrades.

Then a menu/choice is available.

Lots on wheels. Exhausts are in engines.

 

Edited by - Golf Juliet Tango on 10 Oct 2005 20:59:50

[Pete]

I agree with Neil. I made the switch from 15 inch 'Prisoners' to 13 inch rims and the difference in handling was phenomenal. The car felt more alive, more settled on the road and the turn-in was much sharper.

 

I have not had any grounding problems on the open road (in spite of being a lard-a*se). Sleeping Policemen need some care tho'......

 

Do it!

[lancelot]

If the performance increase is down to lower gearing, why not change the diff - that way you can keep your wheels and gain the performance increase.

 

A good set of say A048 may give better cornering too..

[Strangely]

Switching to 13" wheels with CR500's will reduce the rotating unsprung mass significantly. I noticed a huge improvement, and I came from 14" wheels. But... to get the most benefit you might need to adjust the ride height, both for the sake of ground clearance and handling. Do you have adjustable platforms on your dampers (so that you can easily change the ride height of the car)? If not, then a Freestyle suspension upgrade will come in at around the same price . You can also get adjustable platforms for the Bilsteins, but I've no idea what they cost.

[EFA]

A 1.4K engined car will have exactly the same top speed on 13" or 16" wheels. You will have higher engine speed when cruising, but not anything to worry about.

 

The acceleration benefiots will be grater by swapping for smaller wheels, especially if your car is 5speed rather than 6. You will get improved grip, poise and handling - very noticeable even on the road.

 

The exhaust is a good plan if you intend to upgrade the engine toa 1.6 or 1.8 which provide a platform for significantly more power over the 1.4.

 

I'd go for the wheels unless you paln on spending several £ 000's over the next year or so.

[Adam H]

As fas as I know the dampers and platforms etc are standard so am I looking at a lot more expense to get the adjustment?

 

I was thinking about trying to get rid of my wheels and put the money towards a set of the rather nice looking new Caterham Anthracite wheels. However, from what I've just read it might be better to keep the larger wheels for longer journeys and use the smaller ones for blatting. So it looks like second-hand minilites or similar then.

 

Adam

1400ss 6sp

[EFA]

Nope, Sell the 16" wheels and buy the Anthracites. Gearing difference is no so great.

[neil.cavanagh]

how many miles have you on your 7 arnie? 😬 😬 😬

 

having done 20K in 28 months or so I do appreciate the bigger wheels and the more relaxed gearing for the longer runs, (like 400 miles before you get to the fun roads in Jockland) and the smaller wheels for the track.

 

Other thing to consider is tyre cost:

 

13" you can get Yoko 48s for £65 or so a corner. They are great but will last 3-5K miles. On the 16" get something like Toyo T1-S or Scudio Stunners, for £65 a corner also, but they will last 10-15K of spirited driving.

All depends on how much you use the car. If only 5K a year then doesn't matter, but if you do bigger mileage the hassle of changing tyres so oftern, and the cost, adds up.

[Dartmoor7]

If you get tyres other than the CR500s (which look a bit silly on the car in 175/55) the changes to speedo accuracy (such as it is) would be relatively minor.

From 205/45x16

To 185/60x13 -6.5%

Or to 205/60x13 -2.5%

If you fit 185/70x13 A021s the change is zero.

 

I changed from 205/45x16 on my 1400 SS to 185/60x13.

Theoretically ride height drops about 20mm but my suspension is not adjustable and I have no problems.

I wouldn't change back, but if I'd paid Caterham prices for a wheel/tyre package rather than secondhand, I might not have thought the change was worth the money.

I think the biggest difference in changing to 13" is the access it gives you to cheap sticky tyres.

 

 

 

Jerry Parker

L7 SVN

1400 Supersport

 

Edited by - L7SVN on 11 Oct 2005 13:26:33

[EFA]

Neil,

 

You answered your own question "the hassle of changing tyres so often"

 

Do you really sit and look at it from the perspective of "I'm going a long way today, better pop out to the garage, jack up the car, swap the wheels over, then let the Mrs know I'm ready to go. By which time she'll have taken the tintop instead!

 

50k in 10 years

[mav]

Arnie,

 

There are a number of people who do exactly that, and Neil does not have a Mrs to worry about .

 

Even though I now have a Mrs, She would still wait if I needed to swap over wheels / tyres etc...

[EFA]

Wait 'til the honeymoons over..... 😬

 

Edited by - EFA on 11 Oct 2005 11:00:18

[neil.cavanagh]

Arnie,

I do look at it on a 'when am I next planning a long trip' point of view. If in the short term, then the big wheels stay on. If not for a few weeks/month then the small wheels go on.

 

With a nice fancy jack (thanks Norman) and a power drill to help with my nuts (ohhh errr) it doesn't take long to do. Plus most 7 owners will give their car a once over every month (especially before a touring weekend) or so which probably involves taking the wheels off anyway.

 

bringing backa little more in thread... Adam, if you dont' do much/any touring/ weekend trips then feel free to sell the big wheels. Though you will probably only get £1-300 I think, in which case I'd keep them as spares/touring wheels.

[GTD]

Agreed - look at the wheels on the race cars, 13" all round, sir!

 

 

 

G for Geoff

[Ozzy]

I think I'm missing something here. It seems that most of you have gone from large dia wheels with low profile tyres, to smaller dia wheels with higher profile tyres. Arn't you ending up with a similar circumference? So how come you claim better acceleration

 

Please enlighten me.

 

Oz.

 

Still Shaking.

 

6 speed 1600k Supersport

 

[Strangely]

The circumference is similar, but not the same. I went from 14" 185/60 to 13" 175/55 - quite a drop and change to the gearing. Also, the reduction in rotating mass helps acceleration.

[Dartmoor7]

Ozzy, they're talking about improvements measured in tenths of a second (and not very many tenths at that).

 

Jerry Parker

L7 SVN

1400 Supersport

[Ozzy]

Ok Jerry, but another thoughts just struck me. If circumference is similar, how come ride height may differ by 1.5 inches? Still don't see it somehow!

 

Oz.

 

Still Shaking.

 

6 speed 1600k Supersport

 

[Dartmoor7]

Yeah, it would help if people specified the tyres they use not just the wheel size.

The difference is in the tyres; if you fit 185/70x13 there will be no change in ride height, if you fit the 175/55x13 there will be a drop of 34mm.

 

Jerry Parker

L7 SVN

1400 Supersport

[Brucey]

Adam,

 

I had the same dilema as you about 3 months ago on my 1993 14K ss. In addition, I needed 2 x 205/45/16 rear tyres which looked like they were going to be expensive (around £90 each to match the new Goodyear F1's on the front).

 

With the 16" HPC's, I found the steering a bit 'bumpy' especially on uneven road surfaces. I also found myself clenching my buttocks every time I drove over a white line! (even with just 16psi tyre pressure all round). In the wet, I wasn't sure if the car was aqua planing or just floating accross standing water!

 

After receiving much the same advise as you have on blat chat, I decided to go for a slight compromise (you can tell I'm married!).

 

Instead of going 13" wheels shod with road legal racing tyres, I went for second hand 14" Minators (Placed a wanted ad on blat chat) with new 185/60/14 Yokohama A539 tyres.

 

Upside:

I sold the 5 HPC's on blatchat for £250 (with 2 good and 3 iffy tyres fitted) so 5 S/Hand Minitors and 5 new tyres cost me no more than £200 extra.

Note: It would have cost me £180 to replace the 16" back tyres anyway.

I later found 1 of the Minators had a bent rim (now the spare) so check carefully B4 U buy

Price includes £20 for centre caps from George Polley (not supplied with wheels)

The ride quality, bump steer, balance and handling have all been significantly improved.

 

Downside:

This effectively reduced my ground clearance by 10mm - 15mm (tyre diameter and extra tyre 'give')

Speedo is reading about 10% faster (as will odometer be), but judging by driving past those flashing 30mph warning signs, may actually be a bit more accurate 😬(I doubt if Caterham callibrated each car speedo for each wheel size)

My (internal, rear exit) exhaust does ground out more frequently since changing. Although I may replace this with a traditional side exit exhaust (as you already have)to resolve this.

I have holed the sump (repaired by welding). Ground clearance 75mm-80mm now. But I have been practicing driving over 3" rocks to miss the sump!

Raising the ride hight will mean fitting adjustable platforms at another £100+

Some wheel anti theft issues (fitted locking wheel nut to spare, but wheels on car not as anti theft as HPC's)

 

Am I happy with my choice to change 🤔

 

Overall YES 7's are about handling and driving. My car is more fun to drive as a result of changing 😬

 

Hope this helps. If you are still in doubt, either drive my car or sombody elses before you decide

 

Bruce.

 

 

 

 

Brucey

[grumpy the 7th]

Adam

 

As per Brucey I too have JUST changed from 14" 185x60 (pirelli tyres ) to new anthracite 13" 185x60 (AO21's)

 

The car has a much more 'at one with the road' feeling

 

Apart from some teething troubles getting them balanced 🙆🏻 (can't cure a slight wobble at 70 to 80 😳) I've had them done twice 🙆🏻 and had the car laser tracked (it was out but now bang on parallel) I'm working through rotating the wheels front to back to identify a 'rougue wheel'

 

However It definately feels more direct , more planted , and much brisker accelleration

 

I've got the Road Angel which showed my original 14" wheels were causing the speedo to UNDER read by 5% with the new 13" wheels it now slightly OVER reads. (but hey! don't worry about things like that. Just don't get caught 😬)

 

 

rog

C7 TNT - it's Dynamite!(Honda Irish Green and Peugeot Graphite grey)