Why wouldn't this work?

[corksil]

I've been playing with a lot of ideas lately. Help me think this one through and spot anything that I may have missed.

Attracted to a 450 four-stroke single honda (XR450) street legal with turn signals and plates. Water cooled, fuel injected. This would be the base model for the next bike build-up.

Install a big brake kit up front with dual calipers and large twin rotors ala supersport style. For road riding, the bulk of the braking comes from the front wheel.

Pick up a set of aftermarket rims, install the same big brake rotors up front, and put on some radial slick street tires.

Keep the original rims/tires set up with knobbies for off-road riding.

In the rear -- original rims could have shorter gearing rear sprocket aimed toward torque/acceleration.

Rear aftermarket rim (street tire) would be set up with taller rear sprocket aimed toward top speed/high-way cruising.

The plan is to use one bike for off-roading with the knobby rim/tires, and on-roading with the slick street tires. I'd need to adjust the chain as necessary when swapping wheels due to the different rear sprocket sizes.

Why wouldn't this work?

--sprockets/chain should ideally be mated together for life to prolong wear. Riding on the street for extended periods of time would cause the chain/rear sprocket to wear consistently together, so swapping to rear rim with off-road tires/sprocket could potentially exaggerate chain/sprocket wear.

--brakes pads would need to be broken in each time I swapped rims. Brake pads and rotors wear at different speeds, so if I used the street wheel setup for a while and then switched to the dirt wheels, I'd have to do a few high-speed stops to get the brake pads properly bedded into the different rotors.

What else am I missing? There could obviously be an argument about having the suspension set up for road riding and how swapping to dirt tires would make the road suspension setup improper for the traction differences between dirt and tarmac.

As for gearing differences, they wouldn't be ideal for either dirt or tarmac -- but with the power of a 450 I think it would be a worthwhile compromise.

A big brake setup on the front tire would be a little excessive if riding on the dirt, but if it was well put together/designed, it should have enough 'feel' to be manageable.

Feels like I'm overlooking a tiny but very important detail.

[csmith12]

[adouglas]

Aside from the obvious issues with running dirt-optimized suspension on the street (just think for a second about what will happen when you apply those big brakes.... can you say nosedive?) ...

I can think of two considerations:

1) Does this "big brake kit" exist or would it be something you need to create? The OEM rim does not have provision for dual discs, right? Therefore you'll need to source an offroad rim that does and also fits... and I don't think such an animal exists.

Or, you could design such a hub, have it machined and build your own wheel... at which point you might as well just buy a street bike.

Plus you'd need to fabricate some sort of mount for the second caliper. More design and machining.

2) "Hey, looks like it's going to be nice this weekend... let's go dirt riding!"

"Okay, but I'll need to swap wheels first. And when we get home, I'll need time to clean up the bike and swap back."

This can get old pretty quick.


Re bedding in the pads... Not so sure that this is a real issue. Before I bought my track bike I had a second set of wheels with track tires on them. I'd just swap out the street wheels whenever I did a track day... no special "re-bedding." Never had an issue with braking.

[subxero]

the money you would spend in just a nice extra wheel set + all the other stuff you list and you could probably get yourself a decent purposely built off road bike that would be way better at off roading than the xr. JMO. late 90's early 00's 2 strokes are great bikes, cheap to maintain and lacking nowhere and can often be found for $1k sometimes more or less depending on condition and seller. If you want a dual sport though so you can go on and off road at will with no hauling then do what you want, not sure what the off road scene is like where you live. Riding off road bikes without hauling is fairly easy in my parts an non issue. I would probably go with a different bike personally but that is pure personal preference.

["A"]

For Maui, I doubt you meed much of road oriented gearing or braking.. lighter weight vehicle would do much better off-pavement.
You can never have "best for both worlds" on a single vehicle.. compromise one that would make the majority of riding better.. the other just relax riding and get to your destination.. don't try to push the envelope for both types of riding.

[tgold]

Comments. In no particular order:

The rebuild interval for the 450 motor is somewhere between 50 and 60 hours last time I checked. I know this because I raced with a very similar TRX450 motor in a quad in the Baja1000. We actually took longer to finish the race than the recommended rebuild interval. Our motor didn't last the entire race, but truthfully that was really due to the air filter coming loose. Twice. Doh!
Regardless, the lifespan of that Honda 450 motor is relatively short and the rebuild is expen$ive. Not good if you're racking up a lot of hours on the road. Of course the level of use or abuse is the main factor in your motor's lifespan.

No need for a two rotor brake setup. You will have all the brakes that you want with one easily sourced big rotor setup.

The expense of an extra wheelset can easily exceed the cost of a used dirtbike that is in good shape. Less hassle and you have two bikes.

Even so, it's been done many times. If this is what you want to do, I suggest that you check out supermotojunkie.com or thumpertalk.

[subxero]

^ not overly familiar with quads but is the trx450 the race version? Like for bikes the crf450 is the race bike and motor and the xr450 is not the same motor, it is not on the same performance level as the crf motor and the durability, longevity and rebuild intervals are much longer/spaced out.

[SLOWn60]

For the love of all that is good corksil: STOP THINKING!!!


I did this with my CRF450 (not street legal though):

Stock for trail riding/n00b level MX except for suspension springs, airbox tweaks, pink wire, pipe & header, Scott dampner, bars, pegs, yada yada yada

and

A complete suspension swap (forks & shock) tuned for Supermoto, 17" wheels, Brembo front brake/rotor/master, etc.

GAWD I wish Honda would make a street legal CRF 450!

Anyhoo; back on topic: The swaps worked great to effectively give me two killer tools for podium Supermoto and total trail dominance (Pro tip: spoon on a super sticky Trials rear tire! ) However; even though the swaps only take a little over an hour: it soon gets stale in a busy summer of racing & camping/trail riding! One does get extremely fast at swapping shocks and breaking & lengthening/shortening a chain!

Bottom line: I wouldn't do it again. For not much more money once the dust settles; I'd buy & build two separate bikes.

[tgold]

Originally Posted by subxero

^ not overly familiar with quads but is the trx450 the race version? Like for bikes the crf450 is the race bike and motor and the xr450 is not the same motor, it is not on the same performance level as the crf motor and the durability, longevity and rebuild intervals are much longer/spaced out.

There is no XR450. Only the CRF450.

[subxero]

@tgold I didn't even bother to look, but that is what Corksil said in the first post (xr450) street legal. I don't follow much of the Honda lines let alone their xr line. I know their crf is not street legal and takes a fair amount of mods to make it street legal. I know they have an xr650 I think that is fairly current and is street legal dual sport, they had a xr400 in the early 2000's as well but don't think it is offered anymore.

forgot they have their newer crf250L dual sport, our very own @Alex has one of those.

@corksil can you clear this up? what motorcycle were you talking about. If you are talking about the crf450r I agree with Timm, rebuilds are frequent and can be quite costly especially if anything goes.

[tgold]

Originally Posted by subxero

@tgold I didn't even both to look, but that is what Corksil said in the first post (xr450) street legal. I don't follow much of the Honda lines let alone their xr line. I know their crf is not street legal and takes a fair amount of mods to make it street legal. I know they have an xr650 I think that is fairly current and is street legal dual sport, they had a xr400 in the early 2000's as well but don't think it is offered anymore.

forgot they have their newer crf250L, our very own @Alex has one of those.

@corksil can you clear this up? what motorcycle were you talking about. If you are talking about the crf450 I agree with Timm, rebuilds are frequent and can be quite costly especially if anything goes.

I checked just to be sure it wasn't something new and I got nada except for the CRF450R motocrosser and the CRF450X which is a true off-road enduro bike.

[VaFish]

Why not get a Suzuki DRZ400SM and an extra set of wheels/tires?

[tgold]

Originally Posted by VaFish

Why not get a Suzuki DRZ400SM and an extra set of wheels/tires?

I was thinking the same thing. You might even be able to get an OEM set of wheels from the offroad version of the DRZ.

[VaFish]

Originally Posted by tgold

I was thinking the same thing. You might even be able to get an OEM set of wheels from the offroad version of the DRZ.

Very popular thing to do, just need the larger brake rotor of the supermoto on the 21" off road wheel.

Or you run 17" rear off road tires on the front of the supermoto.

[k-os]

Originally Posted by VaFish

Very popular thing to do, just need the larger brake rotor of the supermoto on the 21" off road wheel.

Or you run 17" rear off road tires on the front of the supermoto.

I believe the rear rotor is also a little larger on the SM compared to the S/E.

[corksil]

I believe the CRF450R is an off-road model, never intended for on-road use. Kick-start.

CRF450X was moreso enduro inspired, with electric start and slightly de-tuned toward mid-range performance and top end speed.

In a way, this is a continuation of my "best bike" thread, because people aren't as likely to click on threads with several pages of replies.

My thinking was that I could acquire a street legal CRF450X with lights/license plates and electric start, and then swap over some big brake components and rims designed for the CRF450R.

Things may have changed, so I'll figure it out in the next few days. Time to go for another ride and knock on some doors to inquire whether or not certain bikes have been sold or if they are still available.

[subxero]

Originally Posted by corksil

I believe the CRF450R is an off-road model, never intended for on-road use. Kick-start.

CRF450X was moreso enduro inspired, with electric start and slightly de-tuned toward mid-range performance and top end speed.

In a way, this is a continuation of my "best bike" thread, because people aren't as likely to click on threads with several pages of replies.

My thinking was that I could acquire a street legal CRF450X with lights/license plates and electric start, and then swap over some big brake components and rims designed for the CRF450R.

Things may have changed, so I'll figure it out in the next few days. Time to go for another ride and knock on some doors to inquire whether or not certain bikes have been sold or if they are still available.

I know one of your main goals is performance of the motor but again, the crf450 motors, both the r and the x are practically race engines, they require a lot of up keep at that performance level. Off roaders who are screaming on these non stop are probably doing top ends and more every 20 - 35hrs. Riding one of these on the road is not a terrible idea, would be fun but if I was going to use it for anything more than the occasional weekend ride here and there I would reconsider personally. If your average trip speed is around 30mph that means tearing the top end down for checks, (valves, pistons, rings, cylinder ect...) every 600 - 1000 miles of riding give or take, bottom end every 4000 miles or so give or take. just something to consider. Purposely built dual sports like a drz400 will be much longer service intervals, a little less performance, a little more weight. Although, some of those guys are really into those drz400 SM's and with some decent cash you can get good performance out of them.