How low is to low?????

[FOMOGO]

I am trying to come to a happy medium for ride height on my Warrior project and would like opinions of what is to low for frame clearance. Its going to be a hard surface use bike and I cant see taking it off road. By off road I mean in the woods and through ditches and mud. I am not worried about riding it in the dirt, I just don't intend to use it like a dirt bike. I have other bikes for that. Right now I have it mocked up at 4 1/4'' to the bottom of the frame. It looks mean but I am afraid that it is to low at that number. I had it at 7 1/4'' and it looked like a motocross bike.

Any real world feedback will be very much appreciated.

Thanks,

Doug

7 1/4''

4 1/4''

 

[PAP]

I've put a lot of thought into the same thing this last coupla weeks, after riding my Renegade. After close study of how it handles at all speeds, I and under the notion that the center of gravity is too high. It has about 8" of clearance at it's lowest point, but yet with the angled motor mount that puts the crank height right at 15". I am convinced that if it was at least 2" lower, it would handle better. I have been studying pictures of various bikes, and have come to the conclusion that the top of motor mount plate should be on the centerline of the axles. Most motors have cranks that are 4"-ish from the bottom of the crank case.
My axle height is 8.5", and if I would have mounted the motor horizontal on the centerline, the crank height would be 12.5". Angling the motor mount to put the crank height the same will result in less ground clearance in the front, but I don't think it's that big of deal.
With those big tires, I think you'll be ok if you stayed in the area I described.

 

[David wulf]

Doug I would go with the 7 1/4" height. In that pic your swingarm is level which is where it should be . Also what is the rake of the front end ? for a good handling bike you want in the 25-27 degree range .
I'am in the process of rebuilding a custom Powell that I built a few years ago , it will be my new flat track bike I have dropped it from 11 inches to 9 inches and deraked it from 28 to 25 degrees. The bike has a pitbike suspension on it and it handled great to start with . The 4 1/4 is just to low unless you want to drag race it .
Paps bike as great as it is , is a copy of a RUPP scrambler and they don't handle very well period.
Here are three pics of bikes the first one is a Powell challenger 1970 hands down the best handling minibike ever built . It can be flat tracked or motocrossed and it's great . It sets unweighted at about 7" .
The next pic is the superpowell I built , sits at 11" and 26 degrees rake and handles great . The third pic is the super Powell remodeled the Powell lower frame rails taken off and was drop 3" . When it was dropped the rake changed to 29 degrees, neck was cut and brought to 25 degrees which is perfect for a track bike .

 

[FOMOGO]

[MENTION=55688]PAP[/MENTION] this pic I found on the web has me thinking that I am not to low. But I truly have no clue as to the detriments of being to low, other than dragging the ground when you turn.

I know there has to be a rule of thumb somewhere that is a happy medium. This pic references frame height, axle centerline and engine height.

Its pretty close to where I want mine to sit. I think I am going to rise mine 3/4'' and try working off of a 5'' frame height. Its all still adjustable at this point. I think It will work out at that height.

Doug

 

[Evil Tweety Bird]

Higher the CG point the more responsive the bike would be to input. It will tend to lean over much quicker.
Down low it will tend to fight leaning over.

Actually think pendulum to understand it. The higher you move the weight from the pivot point (tires) the less force is required to move/lean over.

Both up and down have good and bad points. Motocross, up high, is like a skittish horse. Not something you want for a long ride. You'll be fighting it constantly. Something like a Gold Wing, down low, and it will want to go straight and stay upright for a long haul, but don't expect to take it and do well at say Road Atlanta.

One other thing to consider, your foot pegs. Down low and they are that much closer to the catching on the pavement if you really have to lean into a turn.

 

[FOMOGO]

[MENTION=26262]David wulf[/MENTION] you were posting at the same time I was posting. Thank you for the detailed input.

I hear ya on the swing arm. I wish the front mount was a little higher now that its welded like an engine mount for a Locomotive.....

I also follow your reasoning at the 7'' height. I want to say that the rake is 32 degrees. I would have to measure it to make sure.

I just don't like the look at 7''.... And I think the 4 1/4'' is too low as the 420 is wide leading to even wider pegs. I think I am going to set it up at the 5 '' frame height with stiff legs in place of the shocks and set it on the floor so I can see how far it will lean and how it feels.

I am shooting for a big bruising cruiser more than anything. Car shows and swap meets mostly. Not really looking to get to far off the hard pack with it.

I have never owned a running motorcycle so I have no reference as far as riding experience goes. I have owned a whole bunch of Honda 3 wheelers and Honda 4 wheelers. And there is no comparison to 2 wheelers....


Doug

 

[FOMOGO]

Higher the CG point the more responsive the bike would be to input. It will tend to lean over much quicker.
Down low it will tend to fight leaning over.

Actually think pendulum to understand it. The higher you move the weight from the pivot point (tires) the less force is required to move/lean over.

Both up and down have good and bad points. Motocross, up high, is like a skittish horse. Not something you want for a long ride. You'll be fighting it constantly. Something like a Gold Wing, down low, and it will want to go straight and stay upright for a long haul, but don't expect to take it and do well at say Road Atlanta.

One other thing to consider, your foot pegs. Down low and they are that much closer to the catching on the pavement if you really have to lean into a turn.

Thanks Evil this is all new information to me and you have added to what the others have said. Nothing is set in stone yet except the swingarm pivot point... I am still learning.

When you say the higher the CG does this include the rider??? At 6'2'' and 275 I have a high CG.....

Doug

 

[Havasu Dave]

Doug, CG isn't even a factor, unless you're rolling it up towards 50 MPH, AND taking tight turns with it. Those Kenda Speed Racer Pro tires are ATV tires, are not designed for speed turns on two wheels.

We've already discussed steering geometry ad nauseam. There is no lean angle "rule of thumb" because design and purpose factors decide it.

In your chopper drawing above, pegs are placed higher to facilitate clearance. On a mini bike, you don't have that option, unless you're five feet tall.

I don't think you'll have any problems with ground clearance in a lean, even if you tried to have problems. :laugh:

For what it's worth, IMO it looks better, lower. But with the proximity of the driven, I'd go with the higher to give it more room for off road- just in case you do go off road. Moreover, the higher position allows you some leeway with peg mounting that you will not have if it's lower.

 

[FOMOGO]

Doug, CG isn't even a factor, unless you're rolling it up towards 50 MPH, AND taking tight turns with it. Those Kenda Speed Racer Pro tires are ATV tires, are not designed for speed turns on two wheels.

We've already discussed steering geometry ad nauseam. There is no lean angle "rule of thumb" because design and purpose factors decide it.

In your chopper drawing above, pegs are placed higher to facilitate clearance. On a mini bike, you don't have that option, unless you're five feet tall.

I don't think you'll have any problems with ground clearance in a lean, even if you tried to have problems. :laugh:

For what it's worth, IMO it looks better, lower. But with the proximity of the driven, I'd go with the higher to give it more room for off road- just in case you do go off road. Moreover, the higher position allows you some leeway with peg mounting that you will not have if it's lower.

Thanks Dave, all good points but it sure does look mean sitting low.

The driven is only about 1/8'' below the bottom of the frame. I tried hard to keep it up as high as was practical. The plan all along was to use forward mounted pegs with them mounted just about mid way through the up bend in the frame. :shrug: They should allow for leg and foot clearance ahead of the engine plus a slightly higher location.

I think a tacked on stiff leg in place of the rear shocks will tell me a lot when it hits the floor.

The Kendas are pretty easy to get round with a little extra air pressure. Even the wide rear will round out pretty nice. I think part of the reason it will is the narrow width of the rim.

All I know is I am having fun and I haven't gone for a ride yet....

Doug

 

[danford1]

When you do your lean tests for ground clearance keep in mind when your swing arm is compressed you loose ground clearance. If you are turning and hit a hole in the grass or pavement, you could catch a footpeg or your foot.


Just my opinions, others will vary.

Danford1

 

[noseoil]

Doug, I agree with you about the looks & a lower frame, it just looks better that way. As to handling, I guess the only way would be to build it both ways & then decide which is better for what you do with it. My "stock" baja warrior is at about 7" - 8" as it sits, but it isn't really sitting very low for street riding.

I'm inclined to think your 5" dimension is about right for a street bike & should be pretty good. If you aren't going off-road, it shouldn't be an issue. With that height, I don't think the pegs are going to dig in, unless you're almost laying it down into a turn.

 

[PAP]

Higher the CG point the more responsive the bike would be to input. It will tend to lean over much quicker.
Down low it will tend to fight leaning over.

That is exactly what I'm experiencing, but I couldn't tell if it's just that, or the fact that my rake is 30 degrees, or a combo of both. I'm taking this all into consideration for my next build. Also my wheelbase is 44", I did that so I wouldn't have a "wheelie machine".
Doug, what is your wheelbase?

 

[FOMOGO]

Doug, I agree with you about the looks & a lower frame, it just looks better that way. As to handling, I guess the only way would be to build it both ways & then decide which is better for what you do with it. My "stock" baja warrior is at about 7" - 8" as it sits, but it isn't really sitting very low for street riding.

I'm inclined to think your 5" dimension is about right for a street bike & should be pretty good. If you aren't going off-road, it shouldn't be an issue. With that height, I don't think the pegs are going to dig in, unless you're almost laying it down into a turn.

If I am laying down in a turn please help me up because I crashed.......

I have other Baja's to ride in the woods and the mud. I don't need this one to do that. I am going with the 5'' frame height and try it. I think it will be fine for me. I am definitely not an aggressive 2 wheeled rider.

The hard part is going to be shortening the forks 5 or 6 inches to get the front down as far as the rear. I started on a jig fixture this afternoon for it. I will get it welded up in the morning and start slicing and dicing on an extra set that I have.

 

[FOMOGO]

That is exactly what I'm experiencing, but I couldn't tell if it's just that, or the fact that my rake is 30 degrees, or a combo of both. I'm taking this all into consideration for my next build. Also my wheelbase is 44", I did that so I wouldn't have a "wheelie machine".
Doug, what is your wheelbase?

As it sits right now the wheel base is 54''. When I shorten the front forks I figure it will end up about 52''. A stock Warrior is 46''. Rake is 25 degrees.

Doug

 

[dmetcalf69]

Fomogo I love the mock up on this build and at the end of the day I would agree 5" is about as low as I would want to go.
I can't wait to see the end results.

 

[noseoil]

I'll be interested in hearing what it feels like on turns with the lower CG when it's finished. Since you already have a stock warrior, please let us know what you think once it's on the road a for a while. I'm sure it'll feel like a completely different ride with the suspension & swing arm.