Shimano Front Mech Skid Plate: Why?

[CassidyAce]

I trust this is the right section for this query.

I'm installing a new front mech and discovered, for the first time ever, a 'skid plate' on the inner part of the cage: a flimsy bit of poorly attached plastic that looks destined to get mangled or fall off. Why? Shimano, why?

Google gives an inconsistent range of answers. Some say, it improves shifting. Some say, it helps with set up. Some say, it makes the front mech quieter. Some say, it makes no difference and can safely be removed with no effect on shifting. Some say, it's lurking there just waiting to get caught in the chain and cause mischief.

So, three questions: 1) Has anyone figured out what the point of it is? 2) If it's to aid shifting, why use detachable plastic instead of engineering the inner part of the metal cage to create the same profile? 3) If I chuck it in the recycling bin, will I notice any difference when I'm riding?

 

[jonnyboy666]

don't know but . . .

 

[ChromeChainstay]

i just set up a new der. with the plastic insert, makes noise for a 1/3 of the rotation

annoying as hell, quess i'll take it off now

 

[pigman]

i just set up a new der. with the plastic insert, makes noise for a 1/3 of the rotation

annoying as hell, quess i'll take it off now

yep, that' what I found so took it off

 

[pigman]

I trust this is the right section for this query.

I'm installing a new front mech and discovered, for the first time ever, a 'skid plate' on the inner part of the cage: a flimsy bit of poorly attached plastic that looks destined to get mangled or fall off. Why? Shimano, why?

Google gives an inconsistent range of answers. Some say, it improves shifting. Some say, it helps with set up. Some say, it makes the front mech quieter. Some say, it makes no difference and can safely be removed with no effect on shifting. Some say, it's lurking there just waiting to get caught in the chain and cause mischief.

So, three questions: 1) Has anyone figured out what the point of it is? 2) If it's to aid shifting, why use detachable plastic instead of engineering the inner part of the metal cage to create the same profile? 3) If I chuck it in the recycling bin, will I notice any difference when I'm riding?

my theory is if you remember the old days, most front mechs overshifted and thus overshot the big ring. We got round it by just tweaking the outer edge with pliers to stop that overshift. My thought is, this bit of plastic prevents that overshift, thus helping the inexperienced mechanic in setting up and getting it to work successfully. The downside of course it then rubs when in the big ring/small cog combination. I guess Shimano prefer to have something that's going to work easily out of the box and the newby/inexperienced cyclist will just accept the rubbing noise. Given that most sports bikes are now supplied with a 50/11 top gear, it's likely to be seldom used anyway

 

[CassidyAce]

Well... The front mech is fitted, the bike is in use, and the skid plate is... Inoffensive. Nothing annoying but no benefits noticed either. Meh!

 

[FluffyChicken]

my theory is if you remember the old days, most front mechs overshifted and thus overshot the big ring. We got round it by just tweaking the outer edge with pliers to stop that overshift. My thought is, this bit of plastic prevents that overshift, thus helping the inexperienced mechanic in setting up and getting it to work successfully. The downside of course it then rubs when in the big ring/small cog combination. I guess Shimano prefer to have something that's going to work easily out of the box and the newby/inexperienced cyclist will just accept the rubbing noise. Given that most sports bikes are now supplied with a 50/11 top gear, it's likely to be seldom used anyway

Eh, that is what the limit screws are for, any actual over shift was to actually make the shift happen (at least pre ramps and all that). It went a bit over and on release lined up.

 

[FluffyChicken]

P. S. Not really being a road bike person, any pictures of said offending plastic setup, quite interested.

 

[CassidyAce]

P. S. Not really being a road bike person, any pictures of said offending plastic setup, quite interested.

Front view:


Rear, showing retaining clips:


Shimano seems to have put them on all their 2x road and gravel front mechs but not on the 3x ones.

 

[doctor-bond]

Intriguing: I don’t think I would bet my wits against any Shimano techies, but could it be a way of making the chain more ‘sticky’ to pick up? (I suspect function on day 1 rather than on day 3000 was what made it get into the ‘good idea’ bucket.)