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Desert Sleds, Scramblers, 21" front wheels and my RE Interceptor 650

Alan F.

Alan F.

Well-known member
Joined
Feb 12, 2022
Member Number
653
Posts
423
Location
Haverhill, MA, USA
In the absence of any decent videos about scrambler conversions I've been watching videos about vintage Triumph Desert Sleds, not quite the same but better in some ways.

It's got me thinking about a 21 inch front wheel on an Interceptor. The Himalayan uses a 21" front, it's steel from what I've read, 36 spokes like the 650s too. I haven't learned to calculate spoke length for this type of hub, still searching for a good explanation and an online calculator for that.

It would affect road handling, but lots of street bikes use 21" fronts, off pavement it will be much smoother compared to the stock 18" front.

And while I'm not prone to outfit a bike for
"the look I'm going for"
I can't help but think it would look good and ride better everywhere.

Thoughts?
 
I've had several 21" fronts on street bikes and they're not really the handicap that some make them out to be. Traction wise, the contact patch of a larger tire will always be more. The reason sport bikes run smaller tires is for rotating mass. So, yeah, a 21" front might require more bar pressure while countersteering to overcome the extra mass, or it might be slower to react, but it 100% can rail corners with ease.

Case in point. First impressions of comparing my FZ09 with full aftermarket go fast suspension and my '81 XL500S you would assume the modern "sport" bike would far out handle a forty year old dual sport on knobbys. In some ways the FZ09 absolutely does handle better, but there's a tight, twisty goat path of a roughly paved road that the FZ09 handles very well, but my corner speed on the XL was about 10mph faster. It was a 135lb lighter machine. The 18/21 50/59 tires weren't holding it back.
 


Perfect example. Bone stock XR650 on streetish rubber and homie on the sport bike is making all sorts of excuses for why he can't keep up.

NSFW language
 
Last ride with a few Boston friends a few years back one guy was on an XR650L with street tires, there was a slower rider between us and I lost sight of the XR immediately.
I was on a Honda CM400C that I'd synced carbs and tweaked the suspension and brakes, it was the best $600 project I've built yet. If it had a better ignition system I'd have kept it.
(better ignition is available now 😕)
 
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I spotted some mention of RK/Excel offering spoke sets as well so I sent them a message on their website, received a reply this morning that they don't have anything for that bike. I forget the name of the shop in Colorado but they're my next stop before Buchanan's. I'd like to find a spoke length calculator for this type of wheel, its not the regular 90° bend at the head end of the spokes, it's a straight spoke with a very shallow bend at the head end.
Hitchcocks in the UK uses RE's part numbers as their own which can be very convenient at times.

1000003790.jpg
 
Madmx said:
Buchanan will calculate spokes and make a custom set for reasonable money.
Click to expand...
I forgot to mention this, but yeah. They have a huge data base of info. Tell em what hub and rim you got and you're good to go. Not cheap at around $100 per wheel, but I've ordered from them several times and they're always perfect.
 
Alan F. said:
I spotted some mention of RK/Excel offering spoke sets as well so I sent them a message on their website, received a reply this morning that they don't have anything for that bike. I forget the name of the shop in Colorado but they're my next stop before Buchanan's. I'd like to find a spoke length calculator for this type of wheel, its not the regular 90° bend at the head end of the spokes, it's a straight spoke with a very shallow bend at the head end.
Hitchcocks in the UK uses RE's part numbers as their own which can be very convenient at times.

1000003790.jpg
Click to expand...
Pretty typical spoke type for modern hubs. I think we learned that the 90° bends were overkill and the hub/spoke kinda chew each other up that way. The straight-thru like your picture is the norm for dirt bikes anymore
 
I've been measuring my spare 650 front hub and calculating spoke length required to mate the Himmy 21" rim to the Inty hub.

I just ordered up a rim strip to complete the kit, my bargain shopping and a coincidence or two got me a 650 hub, Genuine Himmy front rim, Shinko 244 2.75x21, tube and rim strip, and a set of spokes to try. My running total for this project is just under 3 bills.

I thought I had an "off the shelf" solution for spokes but it turned out that I miscalculated and had to return the first spoke set, so since I'm able to edit my own thread I'll just get rid of the bad info.
 
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Look at your geometry on the Interceptor as stock.
It could be that you can drop your fork tudes in the yokes a few millimeters and and get your geometry back on or at least very close to standard.
your Bike will be way better on rough trails and technical stuff with the front 21.
The Old brit bike deal of 19 inch front was kind of ok but really the 21 or even bigger is the way to go off road.
Do look at sliding the tubes up into the yokes though, it will turn in better left stock its highly probable with the 21 front its going to want to go straight. Just sayin.

An after thought, A wider handlebar is my preference for tougher technical work off road this IMO will help with the 21 inch wheel too.
 
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I picked up a rattle can of Duplicolor wheel paint, I'm hoping their silver will blend in with the stock silver paint on the new rim, hub and fender. Duplicolor says it's OK on plastic hub caps so I'm comfortable using it on the plastic fender. I've got some cast wheels I painted somewhere between 15 - 20 years ago and they still look good.

Wheel Coating – Duplicolor

www.duplicolor.com www.duplicolor.com

Now I just need a warm enough day with no wind.
 
Perfect painting weather this afternoon and I got to it. Just keeping it simple with a Scotchbrite scuff and a BrakeKleen clean before rattle-canning on the Duplicolor Wheel Silver. It's brighter than the RE battleship gray and I'm digging it. I sprayed 2-3pm and I'm thinking of building the wheel tonight.


 
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