Why do they reverse shock's?

[drzdog]

At age 42, I've only been riding for about a year. I've been reading mag.'s ever since to educate my self, and have a lot to learn. So my question of the week is "Why do they reverse shock's???" I notice my humble DRZs has them old stile but all the hot bike's have them reversed.... Hmmmm...

[drjack]

Just guessing, but maybe to have less weight on the part that moves ?

[MXJunky]

MXJunky is unsure of the design benefits of inverted compared to conventional forks, but in the mid-late nineties Suzuki came out with twinwall conventional forks on their MXers that were supposed to be all that, and a bag of chips.

[grayracer513]

Rear shocks were originally "reversed" to reduce unsprung weight. Keeping the weight on the wheel an suspension assemblies that follow the road surface makes it easier for them to do that.

Forks are another matter, since the lower sliders on a "standard" fork are sometimes lighter than the steel fork tubes. If the fork is going to travel 12", there has to be at least that much clearance between the telescoping elements of the fork. Then, there must also be a certain amount of insertion depth of the inner tube into the outer for proper strength at full extension, and enough room must be made for this when bottomed. In a conventional setup, you would also have to add another 8-9" of tube to slip into the triple clamps, but with an inverted fork, that isn't necessary because the outer part is clamped to the steering head, rather than the inner. That allows longer travel without elevating the steering head as far as would be required with "right side up" forks.

?

[RMXC51]

I'm guessing you are actually talking about forks. Forks were inverted primarily to reduce flex over big jumps and SX style obstacles.

[treehuggerssuck]

I'm guessing you are actually talking about forks. Forks were inverted primarily to reduce flex over big jumps and SX style obstacles.

Sport bikes have had inverted forks for ever and I don't think that's the reason why they use them.

[625SXC]

It's a conspiracy by the fork oil companies....It allows the oil to drip out of our KTM forks easier if they are upside down ? Which causes us to buy more fork oil ?

[velosapiens]

Sport bikes have had inverted forks for ever and I don't think that's the reason why they use them.

everything i have ever read has suggested that flex reduction is the main reason for inverting the forks. that way the larger diameter parts get clamped.

[jwriott]

I'm fairly positive there were 2 reasons which both were mentioned.

1. Upside down forks reduced the unsprung mass allowing the fork to absorb smaller bumps better and give the rider more feel.

2. Upside down forks increased the stiffness dramatically buy clamping a much larger, longer tube.

[grayracer513]

I'm fairly positive there were 2 reasons which both were mentioned.

1. Upside down forks reduced the unsprung mass allowing the fork to absorb smaller bumps better and give the rider more feel.

Sometimes. As I said, the weight of the unsprung elements of an inverted fork are not always lighter than the same fork would be as a conventional one. But sometimes it is.

2. Upside down forks increased the stiffness dramatically buy clamping a much larger, longer tube.

The larger clamp section is a benefit. So is the deeper insertion depth I mentioned. Look at your bike (assuming you have inverted forks) and in you mind's eye, take the axle lugs off the bottom, flip them over, and mount them conventionally. See that? the inner tubes are too short to run up into the clamps and still allow 12" between the lower clamp and the dust seals. Inverting them enabled them to be that short. Shorter means overall lighter and lower.

[SDUB]

All of this is true. But the real reason to have upside down forks is marketing. The masses think upside down forks are better, tricker, cooler.... whatever. When upside down forks first became available, you were the man if you had them. It didn't matter that they didn't work as good early on....as long as they were upside down. Now they've got them working as they were supposed to work all along....thankfully. For years though, I missed my '87 CR forks.....

[625SXC]

Scott SUmers took the USD forks off of his new CRF450 and installed the regular forks from an XR650R, So they must still work ?

[jasilva]

Scott SUmers took the USD forks off of his new CRF450 and installed the regular forks from an XR650R, So they must still work ?

However, if you read the article about his bike he stated that he did that because he wanted more flex from his forks.

JOe

[Heckler]

1) Stiffer Design

2) Less unsprung weight

3) Lighter

4) Oil is always at the seals providing better lubrication

5) Larger air chamber

6) looks sick

etc, etc, etc...

[beer_studd_76]

Sport bikes have had inverted forks for ever and I don't think that's the reason why they use them.

actually, it is.

the fat end of the fork will flex less. and from a handling stand point the further the flex is from the wheel, the closer the bike's geometry stays. a tiny flex at the wheel is a tiny flex. a tiny flex at the steering head is a much bigger flex at the wheel.

[iceslice]

Scott SUmers took the USD forks off of his new CRF450 and installed the regular forks from an XR650R, So they must still work ?

His goal was to build a bike that felt like his XR600, and the CRF forks were too stiff. This is a good example of people using what they feel makes them go the fastest. The MX guys feel USD forks work great, so they use them (and the market follows). Summers uses regular forks from an XR, and people are taking note in what he is doing. Its a benifit of enjoying a sport dominated by the guys that race in it =)

[beer_studd_76]

His goal was to build a bike that felt like his XR600, and the CRF forks were too stiff. This is a good example of people using what they feel makes them go the fastest. The MX guys feel USD forks work great, so they use them (and the market follows). Summers uses regular forks from an XR, and people are taking note in what he is doing. Its a benifit of enjoying a sport dominated by the guys that race in it =)

as a general statement, i've always thought conventional forks were nicer in the woods than USDs

[SC_Spode]

as a general statement, i've always thought conventional forks were nicer in the woods than USDs

This is correct ... and why Summers (and yours truly) prefer RSU forks to USD's for off-road. It is the inherent flex characteristics of the the two designs that makes the RSU preferable for many for off-road... it transmits far less of the sharp-edged "shock" to the rider.

I've got two sets of '89 KX 46mm RSU forks that I transplant to different bikes for this reason. Hope to pick up some 96-98 RM Showa TC RSU's soon. Very sweet forks.

?

[CBus660R]

This conversation is very interesting considering I ride a '96 RM250. I'm not a great rider, nor do I ride MX, but when I swap rides with my friends, I can't say that their forks are any better. Now, don't get me started on engine performance ? My 185, I mean 250 is no match for an '05 YZ250.