21 inch front wheel conversion

[Timolgra]

Apart from it's incredible bulk, weight and not having conventional forks I've long suspected the big GS's offroad capabilities are hampered by only having a 19" front wheel.

So I've eventually got around to having a 21" hoop built for my 2005 1150 GSA SE.
I bought a second hand hub which was blasted and powder coated. I asked for the strongest possible rim and spokes.

Building the wheel obviously required great skill.
New 'sleeves' had to be manufactured to hold the inboard nipple into the hub, each spoke required a slight bend just before it entered the hub.

When I first fitted the wheel the spokes just just fouling the inboard edge of both brake calipers
Well there's three ways around that, machine a bit of the caliper mounting fork lugs, machine some of the caliper lugs both of those remedies would require using a washer as a spacer when using my 19" front wheel in the future and of course it would offset the calipers a tad.
So it was out with the angle grinder and with great precision remove the offending material, no problems here, there's plenty of meat there

I fitted new wheel bearings and set off today for a test ride and of course it's always in the back of your mind that the wheel may be all wrong and collapse

Note the front TKC80, much more aggresive that the normal one we use on the GS.
I headed for the mountains in Snowdonia for a road ride test first off, but stopped after a short while to take a photo whilst the bike was still clean

 

[(RIP) ugg]

did ye alter the ratio on the drive , for correct speedo readings?

bike looks shorter , wi larger front tire.
how dose it clear obstacles, itl lift higher on front wont it?

loads of questions ugg

 

[Timolgra]

The roads were covered in this brown slime and salt mix much favoured by motorcyclists but the steering felt good despite my caution which was increased with a brand new knobbly up front.
The steering was perhaps a bit lighter hard to tell really as all my other bikes have 21" fronts wheels which I love.

But this was an exercise in improving it offroad performance so first I thought I'd use some sections of forestry road I know but unfortunately there was too much snow to test it properly, but I have to say the front never stepped out.

Note I had to use a TT Rallye mudguard to give the tyre clearance, I bought this second hand.
The bike just looks right now, which I suppose is a bonus but more importantly, it feels right

 

[Uinneag]

Who done the rim and the respoke Tim

Mind they done a 21in for the 1200 nearly a grand

 

[Timpo]

did ye alter the ratio on the drive , for correct speedo readings?

His bikes are GPS'd to death so they have several speed indicating devices.....

bike looks shorter

It's actually longer......

how dose it clear obstacles

The circumference of the wheel rim is greater so the arc at any particular point is flatter so easier to roll over obstacles. Also the gyroscopic effect of the larger diameter hoop will give more stability when being used on irregular surfaces.

loads of questions ugg

If you don't ask, you'll never know.......

Timpo.

 

[Timolgra]

did ye alter the ratio on the drive , for correct speedo readings?

bike looks shorter , wi larger front tire.
how dose it clear obstacles, itl lift higher on front wont it?

loads of questions ugg

The standard GS speedos read 10% fast, I'm guessing it may be more accurate now but didn't have my GPS on the bike today.

I think it looks shorter in the one photo because the bike is leaning towards the camera.

Yes it does lift the front a bit and I'm just trying to get my head around what would happen if I drop the forks in the bottom yoke.

The main reason for fitting it is an attempt to get the bike to ride over rocks and steps more easily...instead of coming to an abrupt halt if there's not enough momentum but I'm going to have to wait until the snow clears to give it a harder ride.

 

[Timolgra]

Who done the rim and the respoke Tim

Mind they done a 21in for the 1200 nearly a grand

I asked a lot of question before I got it done.
There were companies in Belgium/Holland who I emailed but they were all too expensive.
Tried Central Wheels as you do, but they don't do BM wheels so put me in touch with a small company called Candy wheels based in Kent.
Didn't get the guys name but he was very helpful and knowledgable, he told me he'd built them for Simon Pavey in the past so I began to guess I was dealing with the right guy.
I spoke with him yesterday and told him I'd put some photos up here and it could create a bit of interest.

I supplied the hub and he charged £250, still quite a lot of money but much cheaper than the alternatives, and quite cheap considering the amount of work involved to build it.
The powder coating for the hub was a bit extra.

I've had this wheel built for our trip to Mongolia and Central Asia but need to test it hard before definately using it, ie ride it up and down rock steps and generally try to destroy it, if it holds up then I'll be delighted

 

[wilbjr21]

Well it looks a beautiful job and really solid to boot.

That bikes a credit to you.

 

[(RIP) ugg]

The standard GS speedos read 10% fast, I'm guessing it may be more accurate now but didn't have my GPS on the bike today.

I think it looks shorter in the one photo because the bike is leaning towards the camera.

Yes it does lift the front a bit and I'm just trying to get my head around what would happen if I drop the forks in the bottom yoke.

The main reason for fitting it is an attempt to get the bike to ride over rocks and steps more easily...instead of coming to an abrupt halt if there's not enough momentum but I'm going to have to wait until the snow clears to give it a harder ride.

drop the yokes through the forks? or drop the forks , lower down, am still tryin to figure out the telelever way ov thinkin

 

[Timolgra]

drop the yokes through the forks? or drop the forks , lower down, am still tryin to figure out the telelever way ov thinkin

Dropping the yoke

 

[(RIP) ugg]

yup will gi ye less lift, but wont it turn in tighter?

 

[JohnnyBoxer]

Good to see the finished results, after discussing it at length over the last few weeks

Is it an 21" Excel or Morad Rim?

 

[Timpo]

Good to see the finished results

Yep, fair play... it looks right.

Timpo.

 

[Berin]

devon rim company quoted me about £200 to lace a 21" Morad or £350 to lace a tubeless BMW rim onto an existing hub (1200GSA).

Haven't done it as I was worried about clearance round the fork brace - Wunderlich do a new adjustable one as part of their 21" conversion but it's about £450, they do a mudguard as well.

For the 1200 I think the speedo take off is from the rear wheel.

There's a big thread on it on advrider - a few people have done it, and this Woody guy seems to make some nice hubs. Unfortunately, with him being a septic, he's unable to answer a straight question so I've no idea how much the hubs cost or if you could get him to ship them - but if you look hard enough and wear sunglasses there's quite a lot of info here

Looking forward to see how you get on with it Timolgra

 

[earthmover]

Tim - looks very good indeed, and for all the right reasons. Hope it performs as well as you expect.
Berin - I know its not your fault, but that is the fugliest bike ever.
Mark

 

[vilguy]

Tim- looks mint mate... put me down for one of those!!!

 

[Berin]

Berin - I know its not your fault, but that is the fugliest bike ever.
Mark

mmm -shiny blue crash bars

 

[VAL. H.]

Note the front TKC80, much more aggresive that the normal one we use on the GS.

Looks good Tim

I'm a bit puzzled why you didn't have the 21" BM rim fitted

Surely this would cost no more than the sum of all the extra work involved along with the pain in the arse of having to drag the tube out when you pinch the it on a rock just before the end of a hard day in the saddle in a country thats just too friggin hot to be sitting out in the sun.

An alternative to sliding the forks through the yokes to get rid or some of the excess trail, would be to fit an 18" rim to the rear, giving 'as you know' a greater choice of tyres, but would also raise the rear enough to give back most of the trail angle added to the front when fitting the 21" rim.

Woodies wheels was mentioned above if slightly negatively (re: information) possibly.
I spoke to Woodie a couple of years ago when considering 21/18" conversion for my 1200. He was happy to build the wheels onto BM type rims, thus allowing the retention of the tubeless tyres.
He's not cheep and postage to the UK along with the duty payable would have added something like £400 to the overall cost.

Val.

 

[Timolgra]

Looks good Tim

I'm a bit puzzled why you didn't have the 21" BM rim fitted

Surely this would cost no more than the sum of all the extra work involved along with the pain in the arse of having to drag the tube out when you pinch the it on a rock just before the end of a hard day in the saddle in a country thats just too friggin hot to be sitting out in the sun.

I spoke to Woodie a couple of years ago when considering 21/18" conversion for my 1200. He was happy to build the wheels onto BM type rims, thus allowing the retention of the tubeless tyres.
He's not cheep and postage to the UK along with the duty payable would have added something like £400 to the overall cost.

.

I think you partly answered that yourself. Cost, your quotes are two years old don't forget.

I'm using a 4mm tube and probably won't run it below 22-24 psi so the chances of a compression puncture are (should be) slim.

Fitting an 18" rear is not really a consideration yet, can't afford it anyway. The object of this exercise was only to improve the front of a GS's steering and handling a bit. I've just fitted new Ohlins and the snow's gone so I'll be out on it a few times this week

 

[Timolgra]

DAM, BUG8ER, SOD, FLIPPIN ECK OH DEAREY, feck

It seems that no 21" tyre ie. a Tourance or TKC80 is radial, they're all cross ply which will be much weaker, especially in the event of hitting pot holes whilst using the Tourance during rough road sections particularly in Siberia

So, need a bit more thought and may end up playing it safe using the original 19" front.......oops, possibly the reason BMW don't give 21" front as an option.

This is a great shame since it does handle well offroad. feck