Why the different wheels?

[exiledcarper]

One thing that I've been wondering is just why did R.E. produce the C5 and G (E) 5 with the different sized wheels any way?
  Some have commented that the 18" wheels on the C5 look a bit odd, matched with the high fenders.  I can't help thinking that the bike would look better with 19" wheels, like the G5.
  Is the C5 frame significantly higher?

[ace.cafe]

I don't know the answer.

I could make guesses, but it wouldn't amount to anything valid.

Apparently they just wanted the 18" wheels on the C5 badly enough that they deviated from the 19" that they were already tooled-up and making. So it must have been a pretty good reason.
It would have been cheaper for them to use the 19" wheels that they have been making for years on all the other bikes.
Perhaps the new chassis was designed for 18" wheels.

[Blltrdr]

Exciledcarpenter this is a quote from Vince from an earlier post:

     Please understand that the tire industry has its own logic.
     While 19 and 18 inch tires may have the same NOMINAL size, in practice the 19 inch is smaller.Example: A 19 in. tire that has a "100" mm cross section should be 4 in. wide, but in practice most will measure about 3.5 to 3.75. However an 18" tire with a "100" mm designation will measure out to a full 4 in.  Don't ask me why. This is the way it has been since before I got into this business in 1974.
     The stock 19 in. rear tire on current is a true 3.5 in. width and height for a nominal rolling diameter of 26 in. If the new tire is also a 3.5 in. tire it will be smaller. However these tires are not much more common than the 19 we now use. The common 18 in. rear tire is 4 in. high and wide, giving the same nominal rolling diameter as the 19 in. If they use a metric 100/100-18 we are still near the exact same diameter. Going to a 100/90-18 gives a ride height of 3.5 in., again 1 in. smaller diameter than the current 19.
     So yes, tire choice will have an impact on over all gearing. Four % is a really minor change. It may even enhance top speed by providing enough leverage to pull higher RPM in top gear. You can think this stuff to death. I would suggest seeing if you like it as it comes. If you don't it will be a relatively easy fix.

This may help answer your question. I would have to add that the tire selection for an 18" rim has got to be broader than that of a 19".

Also on a personal note, a set of Dunlop K81 TT100's would look pretty sweet on the C-5 or the G-5 for that matter!

Blltrdr

[Cabo Cruz]

"This may help answer your question. I would have to add that the tire selection for an 18" rim has got to be broader than that of a 19"."  Blltrdr

Ditto.

[UK-Classics]

It's surprising that the 1" difference allows someone like me to get on & off a lot easier - I though I was confined to the world of 'scooters' for the rest of my time   

[exiledcarper]

So more rubber on the road?  Can't argue with that. A lower rear fender would be nice though.

[UK-Classics]

So more rubber on the road?  Can't argue with that. A lower rear fender would be nice though.

Yes - my thoughts entirely when I saw the pics of the rear fender. When you see the bike on the road with a rider (in the flesh) it looks alot better

[t120rbullet]

So more rubber on the road?  Can't argue with that.

I can!
More rubber on the road is not necessarily a good thing.
Just to simplify things lets say your tires have a 4 sq inch contact patch on ea tire. If your bike weighed 200 lbs you would have 25 pounds per sq inch downward force on each tire.
Now when you put your big fat tires on and increased the contact patch to 8 sq inches you would only have 12.5 pounds per sq inch of downward force.

Downward force on the tire is a good thing.

The more surface area you have on the concrete the more heat you create.
Heat is a bad thing.

I have heard the argument that race bikes have these gonzo tires on them so it has to be better. Most race tires have a U or even almost a V shaped profile so the contact patch is small to begin with and as you lay the bike over in a corner the contact patch will remain almost the same size.
And the tires are replaced long before wear changes the profile of the tire.
Most of the bikes with gonzo tires on weigh quite a bit more than our Enfields to start with.

So as far as to why Enfield went with the 18" tires on the C5 I don't know. I doubt if you would be able to tell the difference one way or the other.
The tire selection does not seem to be much better than the 19" ones if you want to stay with matching sets of tires.

If I had my choice I would have had a 3.25 x 19 on the front and a 4.00 x 18 on the back. Just like my Trumps have. Lot's of good tire choices for that combo out there.

All that said I just put a set of Avon RoadRiders on my G5.  90/90 x 19 on the front and 100/90 x 19 on the rear.
The jury is still out on them. I have a few concerns about them that I haven't justified in my mind yet.  I have heard great things about them but............
CJ