How to measure for proper length for a wide glide front end

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paneyes
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How to measure for proper length for a wide glide front end

#1

Post by paneyes » Mon Mar 29, 2010 3:02 am

I have a 51 rigid frame that has been modified ( I know ). I want to put a wide glide front end on but am unsure how to do an accurate measurement for length. The rake is approximately 35-36 degrees with a 1-2 inch stretch. I would like the bike to sit about level with rider, so I am thinking there will be some squat to take into account. Also what years can I use and do I need to use certain triple trees because of the rake? Any help with this issue? Thanks for looking. Steve



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Re: How to measure for proper length for a wide glide front

#2

Post by RUBONE » Mon Mar 29, 2010 4:29 am

Steve,
All that type info is in the old Chopper cookbooks that used to be common. I think you can still get them from Amazon.
Robbie

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Re: How to measure for proper length for a wide glide front

#3

Post by old1955 » Mon Mar 29, 2010 5:09 am

G'day Paneyes,

A couple of things to keep in mind, Harley forks tubes don't run parralell
with the steering stem, they run backwards a little toward the bike, and over a longer distance
this could make a bit of difference to your measurements.

Also early wide glide forks sliders travel 135 mm total, so aim for a 33.5mm sag, which you call squat.
The other name for it. is "ride height". Get your whole bike together and you sit on it, with what
ever you normal carry with you, helmet maybe tools what ever, dial your sag in so it only travels 33.5mm
This is done by altering the spring tension in the fork tubes with spacers, till you get it right.
If you have to cut the spring DON'T. Go find some of those progressive wound springs, they are very short
and make up the spacer to suit. This probably won't happen in an extended fork, the spring will be short anyway.

But I just thought the measurement might be helpful for you to keep in mind.

You could use any triple tree up to the middle eighties I would of thought, but your steering lock hole in the stem
won't be there, but your lock has probable gone on your frame, at a guess.

Pete

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Re: How to measure for proper length for a wide glide front

#4

Post by paneyes » Mon Mar 29, 2010 6:04 am

Pete, I want to take advantage of your information but I do not understand what you mean by the forks not running parallel to the steering head. Could you help me understand this, it sounds like it could make a difference. Thanks

Robbie, thanks for the info.

Steve

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Re: How to measure for proper length for a wide glide front

#5

Post by old1955 » Mon Mar 29, 2010 8:13 am

Set the front end straight on the bike, stand back from any pan or shovel on the left or right of the bike
and look across the fork tubes follow them downward, now follow the line of steering stem downward
and compare that with the line of the tubes, you will notice the forks tubes angle back towards the frame.

These angles on custom springers all run parallel with each other, in Harleys case you could call it
for want of a better term, they de-rake a little as opposed to raked triple trees, but that is not strictly correct.
But you get it now don't you? It is actually to do with trail.


Pete

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Re: How to measure for proper length for a wide glide front

#6

Post by Hauula Pan » Mon Mar 29, 2010 6:07 pm

Due to the rake & stretch you'll probably need to run oversize tubes. I had a frame that had been raked without any stretch and still had to run 2" over tubes to get a level ride height. The over size tubes come with slugs you install on top of the stock length springs and then you fine tune the travel with shim washers. If you already have a glide front end it should be easy to measure how much longer the tubes need to be and then just order the oversize tubes. If you don't have a glide front end yet it is a bit more complicated. You will need to know what size wheel & tire you're going to run both front & rear. You'll need to have the rear installed or at least the frame set on blocks that will give you the same axle heights. With the frame setting level or at the angle you want, you then measure from the axle to the neck and get your overall length. From that you just add or subtract from the stock glide length and order either oversize or undersize tubes to fit your application. Since you are working with both rake & stretch yours will be oversize.

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Re: How to measure for proper length for a wide glide front

#7

Post by paneyes » Tue Mar 30, 2010 2:53 am

Pete, I think I get what your talking about but I don't think I have ever noticed that before. I do not have a glide front end yet so I want to get as close as I can. I have set the frame up with the rear wheel and the frame blocked up to level. When I measure I get 24.25 inches to the bottom neck cup and 31.25 to the top cup. Does this sound right for as much rake and stretch that I mentioned above?

Hauula Pan, thanks for the info. but I don't even know what the stock length is. When you say that I will probably need go to an oversize tube does that just mean length or does it also mean I will need a larger diameter tube? Maybe I am asking for too much, but I would like to get it right the first time.

Thanks to all. Steve

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Re: How to measure for proper length for a wide glide front

#8

Post by Hauula Pan » Tue Mar 30, 2010 7:47 am

Here are some numbers that should help. Stock 1949 FL Frame, Stock 16" wheel & tire, Assembled Glide length from center of axle to top of slider tube at top tree is 28-3/4". The stock inner slider tube is 20" long. the outer lower leg is 15-7/8" overall and 15-1/16" from center of axle to top of outer leg. (On my old raked frame I had to use 22" upper slider tubes to obtain a level ride height.) If you take the 28-3/4 overall length of a stock assembled leg assembly when measured from the center of the axle to the top of the top tree. Use that as your base line, measure a straight line through both your top & bottom tree, (A broom handle works to give a rough straight line that the tubes will follow) measure from the top of your tree to where the center of your axle will be, this will be the overall length you need. subtract the stock 28-3/4" and you'll get how much over stock length your slider tube need to be. Remember the stock 20" slider sits approx. 6-3/4 " inside the 15-7/8" lower leg when assembled which is why the overall length is 28-3/4" and not 35-7/8" Any way the idea is set your frame on blocks to the ride height you want, set the front wheel in line with the broom stick, or measure up from the floor to your axle height if you don't have a wheel, and measure from the top of the top tree to the axle. That's how long your assembled legs will need to be. Knowing that a stock set is 28-3/4" if your measurement is say close to 30-3/4" you know you need 2" over stock, and since stock upper tubes are 20" you would need 22" tubes. 2" over stock. Diameter on stock glide tubes is 41mm. Note: all this changed in the 1980's but no need to go into that. Any way I hope this helps.

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Re: How to measure for proper length for a wide glide front

#9

Post by Hauula Pan » Tue Mar 30, 2010 8:04 am

I noticed you said your measurement from axle to top of neck is 31-1/4" that is approx. 2-1/2" over stock. Take into account that your top tree will add another 1/8-1/4" and some fudge factor you're looking at approx. 2-3/4" over stock. 3" over tubes may sit you just a bit up from level, but 2" over will probably sit you too low. Also take into account you'll get some compression when you add your weight, 3" over might be what you need. Again this all depends on many variables. The rear axle height and front axle height will both depend on what size wheels and tires you run. The overall length of the assembled tubes will depend on if you use stock or progressive springs inside and the length of any slugs and shim washers you use. But using the measurements in my previous post you should be able to get a good estimate of what length tubes you'll need. The lower legs don't change, just the length of the slider tubes is increased. Hope it all works out & this helps some.

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Re: How to measure for proper length for a wide glide front

#10

Post by paneyes » Tue Mar 30, 2010 5:50 pm

Hauula Pan, that was some great information. I should be able to get what I need from that. I will be thinking all this through while setting up a mock front end using 1" PVC pipe (which fits into the neck perfectly). If I can I will take a pic of my mock setup to show how I am doing it. Thanks again. Steve

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Re: How to measure for proper length for a wide glide front

#11

Post by windweaver » Tue Mar 30, 2010 9:23 pm

measuring from the neck will be different than the trees. WW

paneyes
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Re: How to measure for proper length for a wide glide front

#12

Post by paneyes » Tue Mar 30, 2010 11:44 pm

Windweaver, I do not have a front end set up to measure from the triple tree's so I will have to go from the neck cups. Any idea what I would have to add to the distance from lower cup to center of axle to compensate for the triple tree? Any idea what the distance between the neck post and the fork legs? I know it is different for some newer years but I was thinking it must be around 2 to 2.25 inches for the old bikes. Any idea what a good amount of trail would be? Steve

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Re: How to measure for proper length for a wide glide front

#13

Post by paneyes » Wed Mar 31, 2010 3:28 am

This is how I have set up a mock glide set-up for measuring. The two tubes are 2.25" apart center to center ( I think that is how the older trees were set up). The top tube is set at just under 12.5" from the ground (the same as I have for the rear 16" wheel & tire). I measure 24.25" from axle center to lower bearing cup. I am not sure how much to add for the weight of the bike. The lower tube goes to the floor so I could get a fairly accurate measurement for trail. The trail I got for this set-up was 5.5", which might be too much (any idea's on this). Any comments on if I am going at this correctly or not is appreciated. Steve

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Re: How to measure for proper length for a wide glide front

#14

Post by paneyes » Wed Mar 31, 2010 3:30 am

I tried to send 3 pictures but it looks like I did it wrong. steve

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Re: How to measure for proper length for a wide glide front

#15

Post by john HD » Wed Mar 31, 2010 3:38 am

this may help

viewtopic.php?f=33&t=4149

john

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