Carbaugh

[tlanders]

Hi Ron,

Could you help me with my post on rear wheel clearance?

Thanks,

Teddy

[Tony Price]

Teddy,

With my back, knees, and general state of Spodeliness, I try and keep my rear wheel vs ground clearance to zero. []

Glad to be of service.....


Tony

[firstturn]

Teddy,
  Are you picking on me for my Christmas present:).  I hope you and your Family have a Great Christmas and I for one appreciate all you Prayers during the year for downed riders and people that have health issues.  With that said let me see if I can further confuse the situation.
  I know you have several bikes you race and you have told me that you prefer the way one handles over the other.  OK then lets take the one that handles BEST FOR YOU.  Get the bike you have that you like the way it corners and/or handles. Forget about the rear wheel clearance and lets move to the front end as long as the rear tire isn't hitting the frame or fender.
  Go to the front end and measure the rake angle with the bike perpindicular to the horizon.  In other word take a plumb (bob) and drop it straight down to the ground from the top of the steering head of the bike.  Next run a straight edge in a straight line with the angle of the fork legs.  The angle will be measured above the steering head where the two lines meet.  Take this angle and use different length of shocks on your other bikes to achieve the same set up.  Now you can measure the clearance you are talking about.  I will bet you they are all different, but you will have the same geometry on each bike which should make them handle for you.  Remember that all of this predicates on good shocks and good working front ends.
  I hope this sheds some light on-set ups for 4" travel bikes.  The longer travel bikes have a lot more variables.  Just my take and I have been wrong before.[B)]

  Merry Christmas.  I am still looking for Rosemary's hat.  I hope someone finds it in the kitchen stuff that POG has...wouldn't that be great.

Ron Carbaugh

[Dennis Jones]

Teddy, while Ron's way is the correct way to measure rake an easy way is to use a magnetic base angle gauge. Your hardware store will have them for under $10. Just stick it to the steering head and it will give you a reading in degrees. This is how I do trials bikes and for them Ilook for a very steep 21 - 23 degrees.

Dennis Jones

[firstturn]

Dennis,
  Come on I wanted Teddy to have these chalk marks all over his garage floor:).  Dennis is correct (again).

Ron Carbaugh

[rfpotter]

For my own information for when I get my second Penton, and since I shop in the XL section of the department store, if one bike tracks better than the other would I not need to take these measurements when I am on the bike? Would not fork and shock compression alter the geometry?

Going home for Christmas, I can smell Mama's cooking already!

Patrick Houston

[firstturn]

Patrick,

  I like the XL section myself.

  To answer your question for me I measure it both with me on the bike and off.  Read on and please remember that I am telling you this like we would be bench racing at my shop.......
  To be blunt the geometry is changed with every bump you take on a dirt bike.  The world of suspention set up for Bikes isn't a perfect world.  What I try to do (right or wrong for anyone else) is have enough spring front and rear to have the bike set properly (rake angle I want) when setting on the bike stopped on a level surface.  Dampening and shock and front end performance then has to be delt with under the category of oil viscosity for the front verses dampening setting for the rear shocks.
  Just my take and set up falls under the same category of the dreaded subject of what oil mixture is the best.[B)]

Merry Christmas

Ron Carbaugh

[Dave Withrow]

Teddy my friend,
    Don't get too caught up on the rear wheel clearance.  I will say that when I ran a '77MC 400 I went to taller shocks and dropped the front a smidge.  That helped handling a bunch and it was sweet in the turns.  Just my 2 cents.         GO PENTON

MERRY CHRISTMAS EVERYBODY!

[tlanders]

I really appreciate all the advice. Thank you all. However, I wish someone (many) would answer the question. What is the vertical distance on your Penton between the center of the rear axle and the underside of the frame under the seat when the bike is on a bike stand with the rear wheel in the air? I am looking for reference dimensions for the different models. Please record the shock length and which hole they are in. The distance is 16" on my piner that I love. I will do the fork angle measurement also on all the bikes and record them. I realize that this measurement is the bottom line. Thank you for the magnetic base angle gauge recommendation.

MERRY CHRISTMAS

Teddy

[firstturn]

Teddy,
  I am sorry I guess I misunderstood your question.  I am not near any of my Pentons to give you the measurement you are asking for.  I will try to remember to do this for you the next time I am in my shop....do you want the Wassel measurement also;) just kidding.

Ron Carbaugh

[tlanders]

I just went to the lumber yard and bought the magnetic base angle gauge. It was really expensive, OVER $10. ($10.99) I am leaving for Toledo in the morning to be with Rosemary's mom (85 in nursing home) for Christmas. Christina is flying in from California (29) and Alex is driving from Chicago (25). This means that there will be NO measurements until I get back!!! RATS!!! "Visions of fork angles danced through his head"

I love you guys, thanks for all the help. The first guy with a real measurement of the distance gets a can of Kroil Oil the next time I see him.

Teddy

[Dennis Jones]

OK Teddy, here are a couple of measurments I have.

74 1/4 frame with 13.5" stock shocks in the lay down position on stand is 17"

73 175 frame with full width hub, 13.5" works shocks, normal top mount and forward swingarm mount on stand is 15.5"

What I want to know is the combination that will let me ride through the woods as fast as you.

Dennis Jones

[Knute]

Hey Teddy,

74.5 frame is 16.75" with the bike on the stand.  Race sag (same measurement but with bike on the ground and rider in place) would probably be a more relevant number to be comparing though.

Happy Holidays to you and Rosemary!

Kent

[tlanders]

I am on the road on my Treo. I did sneak into the barn before we left this morning and measured some forks. The angles ranged from 28 to 32. When I get settled, I'll fill in the details. Thanks Dennis and Kent for your dimensions. Dennis wins the Kroil Oil, should give you two of them for all the kind words!!! I should stop, this is dangerous. MERRY CHRISTMAS, Teddy

[tlanders]

I got a chance last weekend to do some more measuring. The fork angle results were:
Mint 400 '72 frame, '75 swing arm - 15" shock in hole 1 - 31.5 deg - 55.5"WB - 15.5" AtoF
Mint 400 '72 frame, '75 swing arm - 15" shock in hole 3 - 31 deg - 55.5"WB - 16.75" AtoF
Piner '74.5 stock frame and arm - 14.75" shock in hole 1 - 32 deg - 57.75"WB - 15.125" AtoF
Hare Scrambler - Stock '73 frame and arm - 14.25" shock in hole 3 - 29 deg - 57.75"WB - 16.625" AtoF
1978 MC5 250 - stock frame and arm - 13.625" shock - 58.5"WB - 31.5 deg
1980 MC80 400 - stock frame and arm - 13.875" shock - 58.75"WB - 28.5 deg
1984 MXC 250 - stock frame and arm - standard White Power shock - 58.75"WB - 28 deg

Amazing how different the 1973 Hare Scrambler is from the rest of that era bikes. Mike Lenz says that people didn't like the way they handled. Is that why they went back to the 31/32 deg fork angle from 29 in 1974? How come then do the new bikes have 28 degree fork angles?? Does it have to do with short travel bikes need bigger angles than long travel bikes?

Teddy